Independent of the software development lifecycle followed, it is a good practice to ensure that each test level (e.g., unit testing, integration testing, system testing) has clear and appropriate objectives. This ensures that the testing is focused and effective at each level. Other options either contradict good practices or are not applicable across all lifecycle models.
References:
* ISTQB CTFL Syllabus V4.0, Section 1.4.1 on test levels and objectives, emphasizing the importance of defining clear test objectives for each level of testing.