A reactive test strategy is a test strategy that uses the actual behavior and results of the software under test to design and execute tests, without prior knowledge or documentation of the software1. A reactive test strategy should be utilized for a project that uses a spiral development approach, which is a type of iterative/incremental approach that adds risk analysis and prototyping activities to each iteration2. A reactive test strategy is suitable for a spiral development approach because it allows for flexibility, adaptability, and creativity in the testing process, as well as for early feedback, risk reduction, and continuous improvement in the software development process3. Therefore, option D is the correct answer. Option A is incorrect because a model-based test strategy is a test strategy that uses models to represent the desired behavior and structure of the software under test, and to derive test cases, test data, test procedures, and test oracles. A model-based test strategy may not work well with a spiral development approach, as it requires the availability and stability of the models, which may not be the case in a spiral development approach that involves frequent changes and refinements of the software under test. Option B is incorrect because a methodical test strategy is a test strategy that uses predefined test methods, techniques, and procedures to design and execute tests, such as equivalence partitioning, boundary value analysis, or decision table testing. A methodical test strategy may not work well with a spiral development approach, as it requires the availability and stability of the test basis, such as the requirements, specifications, or design documents, which may not be the case in a spiral development approach that involves frequent changes and refinements of the software under test. Option C is incorrect because a standard-compliant test strategy is a test strategy that follows a predefined set of standards, guidelines, or regulations to design and execute tests, such as ISO, IEEE, or CMMI. A standard-compliant test strategy may not work wellwith a spiral development approach, as it requires the compliance and consistency of the testing process, which may not be the case in a spiral development approach that involves frequent changes and refinements of the software under test. References: 1: ISTQB Glossary, Reactive Test Strategy 2: ISTQB Glossary, Spiral Model 3: ISTQB Advanced Level Test Manager Syllabus, Section 1.1.1 : Spiral Model in Software Development Life Cycle - Software Testing Material : Spiral Model - Tools QA : Strategic Test Management - ISTQB not-for-profit association : ISTQB Glossary, Model-Based Testing : ISTQB Glossary, Methodical Test Strategy : ISTQB Glossary, Standard-Compliant Test Strategy : ISTQB Foundation Level #39 – Test Approach and Strategy - Software Testing Mentor