Explanation / Rationale

Considering:

• The test basis for acceptance testing is the user’s business needs (1D)
• Communication between components is tested during component integration testing (2B)
• Failures in logic can be found during component testing (3A)
• Business rules are the test basis for system testing (4C)

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

a) Is not correct. Priorities for user stories are determined by the business representative together with the development team
b) Is not correct. Testers focus on both functional and non-functional aspects of the system to be tested
c) Is correct. According to the syllabus, this is one of the ways testers add value to iteration and release planning
d) Is not correct. Early test design is not part of release planning. Early test design does not automatically guarantee the release of quality software

Explanation / Rationale

a) Is not correct. This is important, but not as important as test environment elements
b) Is correct. The important thing that is missing is the identification of the browser and device used for the testing. The browser and device information are important because such a defect can be browser- or device-specific. For example, a login button may work fine on one browser (or one version of a specific browser) but not on another. Therefore, the browser and device information can help the developers to reproduce the issue and find the root cause of the problem more quickly
c) Is not correct. The test object is identified (WebShop v0.99)
d) Is not correct. The impact is included – this is severity (high)

Explanation / Rationale

a) Is correct. The ‘tests wear out’ principle is concerned with the idea that repeating identical tests on unaltered code is unlikely to uncover novel defects and therefore, modifying tests may be essential. By using high-level test conditions to generate new tests each time, the tests will not be identical and should not ‘wear out’
b) Is not correct. The ‘absence-of-defects fallacy’ principle is concerned with ensuring that users’ needs are fulfilled even if lots of testing is done and no defects are found (i.e., validation is also necessary). The use of high-level test conditions to generate test cases and execute tests does not directly address this concern
c) Is not correct. The ‘early testing saves time and money’ principle is concerned with fixing defects early on to prevent the occurrence of subsequent defects in derived work products, thereby reducing costs and the likelihood of failures. This is typically addressed by starting testing (both static and dynamic) as early as possible, but this is not addressed by using high-level test conditions to generate test cases and execute tests
d) Is not correct. The ‘Defects cluster together’ principle is concerned with the distribution of defects in a system, which typically follows a Pareto distribution. The use of high-level test conditions to generate test cases and execute tests does not address this concern, which is typically addressed by risk-based testing

Explanation / Rationale

a) Is not correct. When a user reports a software failure, thanks to the unique identification of commits, it is possible to reassemble the files from the software version which was used by the user (as well as the corresponding versions of the test scripts) and thus reproduce the failure and locate the defect faster
b) Is not correct. If a change to the test environment causes unexpected issues during testing, configuration management allows testers to roll back to a previous version of the environment. This ensures that testing can continue without being affected by the change
c) Is not correct. Configuration management ensures that all identified documentation (e.g., requirement specifications) and software items are referenced unambiguously in test documentation (e.g., test plans)
d) Is correct. This is ensured by the defect management, not configuration management process

Explanation / Rationale

a) Is not correct. Component Test-Driven Development is not a correct example of a test-first approach to development
b) Is not correct. Integration Test-Driven Development is not a correct example of a test-first approach to development
c) Is not correct. System Test-Driven Development is not a correct example of a test-first approach to development
d) Is correct. Acceptance Test-Driven Development (ATDD) is a well-known example of a test-first approach to development

Explanation / Rationale

From the graph we have:

A(4)=6 and A(3)=8 (the last two gray boxes).

From the formula we obtain:

E(5) = (3*A(4) + A(3)) / 4 = (3*6+8) / 4 = 26 / 4 = 6.5 person-days.

Thus:
a) Is not correct
b) Is not correct
c) Is correct
d) Is not correct

Explanation / Rationale

a) Is not correct. Quality control applies to all development activities, meaning that every software development activity has a corresponding test activity. However, here we are attempting to equate test levels with development levels, and, although we know what is meant by ‘test levels’, there is no common understanding of the term ‘ development level’
b) Is not correct. Every software development activity has a corresponding test activity; however test objectives are quite different. For instance, there might be a test objective of ensuring that a test object adheres to a contractual requirement that a certain type of testing must be performed before delivery. In this case there is no reason for there to be a corresponding development objective
c) Is not correct. Quality control applies to all development activities, meaning that every software development activity has a corresponding test activity. However, the same symmetry does not apply to testing and user activities. For instance, for some systems it is difficult to even identify the end users. Also, some test activities are focused on developers (e.g., testing for ease of maintainability), which has no user aspect to it
d) Is correct. Quality control applies to all development activities, meaning that every software development activity has a corresponding test activity

Explanation / Rationale

a) Is correct. Obtaining feedback from stakeholders early and often in the software development process can be highly beneficial. It facilitates early communication of potential quality issues, can prevent misunderstandings about requirements, and ensures that any changes in stakeholder requirements are understood and implemented sooner
b) Is not correct. The feedback is from stakeholders, and them providing feedback is unlikely to improve their understanding of their own user requirements
c) Is not correct. Obtaining feedback from stakeholders early and often in the software development process can be highly beneficial. It facilitates early communication of potential quality issues, can prevent misunderstandings about requirements, and ensures that any changes in stakeholder requirements are understood and implemented sooner. However, because changes in requirements can be understood and implemented sooner, it does not mean that unlimited changes to requirements are encouraged
d) Is not correct. The feedback is from stakeholders and does not cover communication to them. Communications to end users could include them being told about which requirements will not be implemented prior to release, but ideally this should not happen at all

Explanation / Rationale

a) Is not correct. The miscalculation of bonuses is a failure by the system, not a defect
b) Is not correct. The system not suitably supporting disabled users is a failure which eventually results in a fine, but the fine itself is not a failure (it appears to be the correct functioning of the regulatory system)
c) Is correct. The error is made by the programmer and this mistake is caused by them working under severe time pressure, which is the root cause of the subsequent defect
d) Is not correct. The poor design of the user interface, which does not suitably address disabled users, is a design defect caused by the designer error. Thus the design of the user interface includes a design defect not a designer error

Explanation / Rationale

Branch testing is a white-box test technique in which the coverage items are branches. A branch is a transfer of control between two nodes in the control flow graph, which shows the possible sequences in which source code statements are executed in the test object. Each transfer of control can be either unconditional (i.e., straight-line code) or conditional (i.e., a decision outcome). Coverage is measured as the number of branches exercised by the test cases divided by the total number of branches, and is expressed as a percentage.
Thus:
a) Is not correct. A decision outcome is a conditional branch. For branch testing, X counts not only conditional, but also unconditional branches
b) Is not correct. Branch coverage counts not only conditional, but also unconditional branches
c) Is correct. Branch coverage is measured as the number of branches exercised by the test cases divided by the total number of branches, and is expressed as a percentage
d) Is not correct. Both X and Y count only conditional branches and do not take into account the unconditional branches

Explanation / Rationale

a) Is not correct. The approval of the budget is an example of an entry criterion. It would make no sense to approve the budget for some activity that has already been done
b) Is correct. Running out of budget can be viewed as a valid exit criterion
c) Is not correct. Availability of resources is an example of an entry criterion for testing
d) Correct. Coverage is a measure of thoroughness, so it is a typical exit criterion
e) Is not correct. This is an example of an entry criterion, checked before the project starts

Explanation / Rationale

a) Is not correct. It is often possible to use dynamic testing to cause a test object to fail in ways that could never be achieved by the users, such as by using fault injection. However, if the failure can never occur with real end users, then identifying it is not especially valuable as testing is ultimately aimed at improving the work product for the end users. Spending time testing for failures that cannot occur with real users is not an efficient use of a tester’s time
b) Is not correct. Static testing in the form of static analysis is used by developers to identify defects in their program code earlier than can be achieved through dynamic testing. Note, however, that static testing (and static analysis) is used to detect defects, not failures, which are found by dynamic testing. Thus it is the use of the term ‘failures’ that makes this an incorrect option
c) Is not correct. Static analysis directly detects anomalies in code, which may be defects, and this is normally for the developer, not the customer. The provision of evidence for release by the use of static analysis of elements that provide no output is nonsense
d) Is correct. Reviews are a form of static testing that can be applied from the very start of the software development lifecycle and are used to find defects that can be removed before subsequent development activities waste effort on faulty requirements. If the defects are not detected and removed early on, then when the defect is found derived work products, such as the design and code, will need to be changed as they were based on faulty requirements

Explanation / Rationale

a) Is not correct. Feedback can improve the test process, but if one only wants to improve future projects, the feedback does not need to come early or frequently
b) Is not correct. Feedback is not used to prioritize requirements
c) Is not correct. The quality of changes can be measured in multiple ways
d) Is correct. Early and frequent feedback allows for the early communication of potential quality problems

Explanation / Rationale

a) Is not correct. Risk management consists of risk analysis and risk control. Neither of these activities supports the reassembly of the files that made up the release, because these activities deal with risks, not with configuration items
b) Is not correct. Test monitoring is concerned with gathering information about testing. This information is used to assess test progress and to measure whether the test exit criteria or the test tasks associated with the exit criteria are satisfied, such as meeting the targets for coverage of product risks, requirements, or other acceptance criteria. Test control uses the information from test monitoring to provide, in the form of control directives, guidance and the necessary corrective actions to achieve the most effective and efficient testing. None of these activities deal with the management of configuration items
c) Is not correct. The whole-team approach builds on the tester’s skill to work effectively in a team context and to contribute positively to the team goals. So, it focuses on team-related issues, not on configuration items
d) Is correct. Configuration management provides a discipline for identifying, controlling, and tracking work products. Configuration management keeps a record of changed configuration items when a new baseline is created. Using configuration management, it is possible to revert to a previous baseline in order to reproduce previous test results

Explanation / Rationale

a) Is not correct. Most work products can be examined using some form of static testing, and a contract must be interpretable by humans and so could be reviewed, which is a form of static testing
b) Is not correct. Most work products can be examined using some form of static testing, and a test plan must be interpretable by humans and so could be reviewed, which is a form of static testing
c) Is correct. Most work products can be examined using some form of static testing; however it is not suitable for work products that are too complex for human interpretation and should not be analyzed by tools, and encrypted code is too complex for humans and if it is properly encrypted it will not be analyzable by most tools
d) Is not correct. Most work products can be examined using some form of static testing, and a test charter must be interpretable by humans and so could be reviewed, which is a form of static testing

Explanation / Rationale

a) Is correct. This principle means that if the same tests are repeated over and over again, eventually these tests no longer find any new defects. This is probably why the tests all passed in this release as well
b) Is not correct. This principle says about the mistaken belief that just finding and fixing a large number of defects will ensure the success of a system
c) Is not correct. This principle says that a small number of components usually contain most of the defects
d) Is not correct. This principle states that testing all combinations of inputs and preconditions is not feasible

Explanation / Rationale

a) Is not correct. Risk monitoring is part of risk control, not risk analysis
b) Is not correct. Risk identification itself does not allow us to implement risk mitigation activities. The mitigating actions are defined during the risk control phase
c) Is correct. This is an example of how risk analysis influences the thoroughness and scope of testing
d) Is not correct. Coverage items are derived using test techniques, not through risk analysis

Explanation / Rationale

Considering each of the listed example defects:

i. Two different parts of the design specification disagree due to the complexity of the design – this is an example of a specification defect, which includes inconsistencies, ambiguities, contradictions, omissions, inaccuracies, and duplications, which can most easily be found by static testing
ii. A response time is too long and so makes users lose patience – this is an example of a response time defect, which can only be detected in practice by executing the program and measuring the response time, which can most easily be found by dynamic testing
iii. A path in the code cannot be reached during execution - this is an example of a coding defect, which includes variables with undefined values, undeclared variables, duplicated or unreachable code, and excessive code complexity, which can most easily be found by static testing
iv. A variable is declared but never subsequently used in the program - this is an example of a coding defect, which includes variables with undefined values, undeclared variables, duplicated or unreachable code, and excessive code complexity, which can most easily be found by static testing
v. The amount of memory needed by the program to generate a report is too high – this is an example of a performance defect, which can only be detected in practice by executing the program and measuring the memory used, which can most easily be found by dynamic testing

Thus:
a) Is not correct
b) Is not correct
c) Is not correct
d) Is correct. The correct match for static testing is i, iii, and iv

Explanation / Rationale

a) Is not correct. In most cases both black-box test techniques and experience-based test techniques can be used for the same test objects
b) Is not correct. Both black-box test techniques and experience-based test techniques can be used at all test levels
c) Is correct. Black-box test techniques (also known as specification-based techniques) are based on an analysis of the specified behavior of the test object without reference to its internal structure. So, the test basis is usually a specification. Experience-based test techniques effectively use the knowledge and experience of testers for the design and implementation of test cases. This means that the tester, when designing tests, may not use the specification at all
d) Is not correct. Experience-based test techniques can detect defects that may be missed using black-box (and white-box) test techniques. Hence, experience-based test techniques are complementary to black-box test techniques and white-box test techniques and both black-box test techniques and experience-based test techniques can be used in all SDLCs

Explanation / Rationale

a) Is not correct. This is an example of a risk monitoring activity, not risk analysis
b) Is not correct. This is an example of an architectural decision, not related with testing
c) Is not correct. This is an example of performing a quantitative risk analysis and is not related to thoroughness or scope of testing
d) Is correct. This shows how risk analysis impacts the thoroughness of testing (i.e., the level of detail)

Explanation / Rationale

a) Is not correct. In exploratory testing, test cases are usually created during the exploratory testing session, alongside test analysis, test implementation and test execution
b) Is not correct. In exploratory testing, tests are simultaneously designed, executed, and evaluated while the tester learns about the test object
c) Is not correct. Exploratory testing results depend heavily on the tester’s experience, so even if the results of exploratory testing can be used as a predictor of risk and used to assess whether there will be fewer or more defects, for example, compared to the previous exploratory testing session, they are not a good example of reliable defect prediction models that can predict the number of remaining defects
d) Is correct. During exploratory testing, the testers can use any techniques that they find useful

Explanation / Rationale

a) Is not correct. Scope creep is an example of a project risk related to technical issues
b) Is correct. Poor architecture is an example of a product risk since it refers to a product characteristic
c) Is not correct. Cost-cutting is an example of a project risk, related to organizational issues
d) Is not correct. Poor tool support is an example of a project risk related to technical issues
e) Is correct. Response time too long is an example of a product risk since it refers to a product characteristic

Explanation / Rationale

a) Is not correct. Test environment readiness is a resource availability criterion; hence it belongs to the entry criteria
b) Is not correct. This is a resource availability criterion; hence it belongs to the entry criteria
c) Is correct. Estimated defect density is a measure of diligence; hence it belongs to the exit criteria.
d) Is not correct. Requirements translated into a given format result in testable requirements; hence it belongs to the entry criteria
e) Is correct. Automation of regression tests is a completion criterion; hence it belongs to the exit criteria

Explanation / Rationale

a) Is not correct. Tracking test progress and identifying areas that require further attention is an example of supporting the ongoing control of testing. This is one of the purposes of test reports
b) Is not correct. Providing information on the tests executed, their results, and any issues or defects found is an example of summarizing the test activities performed at a given test level. This is one of the purposes of test reports
c) Is correct. Providing information about defects is the purpose of a defect report, not a test report
d) Is not correct. Providing information on testing planned for the next period is one of the purposes of test reports

Explanation / Rationale

a) Is not correct. Although it is correct to say that in Agile software development, some of the test management tasks may be handled by the Agile team itself, the testing role is not primarily the responsibility of a single individual from outside the team. Instead the testing is more likely to be performed by various team members following the whole-team approach
b) Is not correct. The test management role primarily involves activities related to test planning, test monitoring and control, and test completion. So, although this statement is partially correct, it is wrong to say that the testing role is primarily responsible for test monitoring and control
c) Is correct. In Agile software development, some of the test management tasks may be handled by the Agile team itself. However, for test activities that span multiple teams within an organization, test managers outside of the development team may perform these tasks
d) Is not correct. The test management role primarily involves activities related to test planning, test monitoring and control, and test completion, while the testing role is primarily responsible for the technical and engineering aspects of testing, such as test analysis, test design, test implementation, and test execution. Thus the test management role is not normally responsible for test analysis and test design, although it is correct to say that the testing role is primarily responsible for test implementation and execution

Explanation / Rationale

a) Is not correct. The detection of additional high-severity defects would be a benefit of test automation, rather than a risk
b) Is not correct. The provision of measures that are too complicated for humans to derive themselves is normally considered to be a benefit of test automation
c) Is correct. If the test automation is incompatible with the development platform, then it will not be able to integrate them, and, for instance, pass test inputs to the test object and receive test results from the test object
d) Is not correct. Substantially reduced test execution times would normally be considered a benefit that is provided by test automation

Explanation / Rationale

a) Is not correct. The organization’s marketing team is unlikely to perform much testing (although in some organizations they may be involved with acceptance testing), so their average level of experience (most of which would be in marketing) is not likely to impact how testing is performed for a given test object
b) Is not correct. The level of knowledge of users that a new system is being built for them is unlikely to affect how testing is performed. Any user involvement that could affect how testing is performed is more likely to be as a result of decisions made by the testers, customer and project manager
c) Is correct. The number of years’ experience of the members of the performance testing team will help to determine the capabilities and knowledge (e.g., of different tools and defect types) that the team members will apply when they are testing
d) Is not correct. The organizational structure of the different end users (who may be varied) will change between users. So, it may not even be known when the application is being tested, and the end user’s organizational structure can thus have little effect on how the testing is performed

Explanation / Rationale

Considering each of the listed benefits and drawbacks of the independence of testing:

i. Ideally, we want close collaboration between testers and developers, which is not increased by isolation. Thus, this is a disadvantage
ii. Testers and developers have varied backgrounds, technical viewpoints, and potential biases, allowing testers to usefully challenge assumptions made by stakeholders during system specification and implementation. Thus, this is an advantage
iii. The main disadvantage of independence in testing is that testers may become isolated from the development team, leading to communication problems, a lack of collaboration, and potentially an adversarial relationship, with testers being blamed for delays and bottlenecks in the release process. Thus, this is a disadvantage
iv. One of the disadvantages of independence in testing is that testers may become isolated from the development team, leading to developers feeling less accountable for quality. Thus, this is a disadvantage
v. The primary benefit of independence in testing is that testers are more likely to identify different types of failures and defects compared to developers, due to their varied backgrounds, technical viewpoints, and potential biases, including cognitive bias

Thus:
a) Is not correct
b) Is correct. The list entries showing benefits are ii and v
c) Is not correct
d) Is not correct

Explanation / Rationale

a) Is not correct. To ensure successful reviews, it's important to secure management's support for the review process, however that does not mean that they should participate as reviewers
b) Is correct. To ensure successful reviews, it's important to break the work product into parts that are small enough to be reviewed in a reasonable timescale to prevent reviewers from losing focus during individual review or review meetings
c) Is not correct. To ensure successful reviews, it's important to clearly define objectives and measurable exit criteria, without evaluating participants
d) Is not correct. To ensure successful reviews, it's important to break down the review into smaller chunks to prevent reviewers from losing focus during individual review or review meetings. So you should not plan to cover one document per review

Explanation / Rationale

The following three transitions:

“REQUESTING -> CONFIRMED”
“WAITING LIST -> CONFIRMED”
“WAITING LIST -> END”

cannot appear in the same test case, which suggests that at least three test cases are required. All the other transitions can appear in combination with one or more of these three transitions, so we need a minimum of three test cases. In fact, only three sequences are possible:

TC1: START (Room request) → REQUESTING (Available) → CONFIRMED (Pay) → END
TC2: START (Room request) → REQUESTING (Not available) → WAITING LIST (Available) → CONFIRMED (Pay) → END
TC3: START (Room request) → REQUESTING (Not available) → WAITING LIST (Cancel) → END

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

Consider:

i. Is true. Faster product release and faster time to market is an advantage of DevOps
ii. Is false. Typically, we need less effort for manual tests because of the use of test automation
iii. Is true. Constant availability of executable software is an advantage
iv. Is false. More regression tests are needed
v. Is false. Not everything is automated and setting up a test automation framework is expensive

Thus:
a) Is not correct
b) Is not correct
c) It is correct
d) Is not correct

Explanation / Rationale
a) Is not correct. Retrospectives are used to capture lessons learned and to improve the development and testing process, not to document the acceptance criteria
b) Is correct. This is the standard way to document acceptance criteria
c) Is not correct. Verbal communication does not allow to physically document the acceptance criteria as part of a user story (”card” aspect in the 3C’s model)
d) Is not correct. Acceptance criteria are related to a user story, not a test plan. Also, acceptance criteria are the conditions that have to be fulfilled to decide if the user story is complete. Risks are not such conditions

Explanation / Rationale

a) Is correct. Test design involves using test conditions to create test cases and other necessary testware, such as test data requirements and test charters for exploratory testing. Test environment requirements are also specified, including the necessary infrastructure and tools
b) Is not correct. Test execution involves executing test cases (as part of test procedures), however it does not directly cover the other testware mentioned in the question, such as test data requirements, test environment requirements and test conditions
c) Is not correct. Test analysis is used to identify the features that require testing. The test basis is analyzed and defined as test conditions, which are then prioritized along with related risks. While this activity involves working with test conditions, it does not cover the other testware mentioned in the question, such as test data requirements, test environment requirements and test cases
d) Is not correct. Test implementation includes the generation of test procedures, such as manual and automated test scripts, which are created from test cases and may be assembled into test suites. Test procedures are prioritized and arranged in a test execution schedule. Test data is created, and the test environment built, and its set up verified. While this activity involves explicitly working with test cases, and may use test data requirements and test environment requirements to create test data and the test environment, it does not cover test conditions

Explanation / Rationale

a) Is correct. Product quality metrics measure quality characteristics. Mean time to failure measures maturity, so it is a product quality metric
b) Is not correct. This is an example of a defect metric, not a product quality metric
c) Is not correct. This is an example of a coverage metric, not a product quality metric
d) Is not correct. This is an example of a defect metric, not a product quality metric

Explanation / Rationale

We want to run test cases according to their priorities, but we also need to consider the dependencies.
If we only consider priorities, we want to first run TC 5 and TC 7 (highest priority), then TC 1, TC 3, and TC 4, and finally TC 2 and TC 6 (lowest priority).
However, in order to run TC 7, we need to first run TC 4.
In order to run TC 5, we need to run TC 4 and TC 2, but TC 2 is blocked by TC 1, which should be run prior to TC 2.
So, in order to run priority 1 test cases as early as possible, the first five test cases should be: TC 4 - TC 7 - TC 1 - TC 2 - TC 5.
Next, we need to run TC 3, because it has higher priority than TC 6.
Thus the full schedule will be TC 4 – TC 7 – TC 1 – TC 2 – TC 5 – TC 3 – TC 6.
So, the sixth test case will be TC 3.

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

Test TC 001 must come first, followed by TC 002, to satisfy dependencies. Afterwards, TC 003 to satisfy priority and then TC 004, followed by TC 005.
Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

a) Is correct. This test case is related to acceptance criteria 2 and 3, because we check if we can set price range (acceptance criterion 2) and if the results update dynamically after adjusting the price range filter (acceptance criterion 3)
b) Is not correct. This test case is not related to any of the acceptance criteria. It checks if the filter dynamically sets the default minimum and maximum price range, and not that a customer can do it
c) Is not correct. This test case is not related to any of the acceptance criteria. It checks the currency exchange feature, which is not discussed in this user story
d) Is not correct. This test case is not related to any of the acceptance criteria. It checks the application’s compatibility with different browsers, which is not discussed in this user story

Explanation / Rationale

a) Is not correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach. If they waited until the next development phase, then unnecessary development (and test) work could be started on unreviewed, flawed work products
b) Is correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach
c) Is not correct. Testers typically review work products that form the test basis as part of test analysis, not before test analysis and design
d) Is not correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach. Waiting until they are published means that any defects that could be found by tester review will be in the published document

Explanation / Rationale

a) Is not correct. A line with a defect, when executed, does not have to cause a failure. For example, a line x := y / z will cause a failure only when z equals 0
b) Is not correct. 100% statement coverage does not guarantee 100% branch coverage. For example, a test case with x=0 for the code

1. IF (x=0) THEN
2. A;
3. ENDIF

achieves 100% statement coverage but does not cover the branch from 1 to 3
c) Is correct. 100% statement coverage means that each executable statement was executed at least once
d) Is not correct. The removed test case may provide coverage of some statements that are not covered by either of the other two test cases, in which case the remaining two test cases together will not achieve 100% statement coverage