Which testing type focuses on verifying that the system functions fulfill user and task objectives?

Suitability testing is specifically designed to verify whether a system meets the needs of its users and effectively fulfills the intended tasks. This testing type evaluates how well the features of the application align with user requirements and if they provide the expected functionality. It ensures that the application is appropriate for its intended use and can achieve the desired outcomes from the user's perspective.

In the context of Agile testing, suitability testing emphasizes understanding user needs and how well the system satisfies these needs, marrying user objectives with system capabilities. This makes it a critical part of ensuring software serves its intended purpose effectively.

Other testing types mentioned serve different objectives; for instance, regressive testing focuses on ensuring that recent changes do not adversely affect existing functionality, while exploratory testing is about unscripted testing to discover issues and understand the system's behavior. Performance testing, on the other hand, evaluates the responsiveness and stability of the system under load but does not directly assess user and task objectives. Thus, suitability testing is the most relevant choice in this scenario.