When can functional and structural testing BOTH be applied?

Functional and structural testing can both be applied at all test levels, from component testing to acceptance testing1 . Functional testing verifies whether the software meets the specified requirements and user expectations, while structural testing verifies whether the software meets the specified design and code standards1 . Both types of testing can be useful at any stage of the software development life cycle, depending on the test objectives and scope1 . The other options are incorrect, because they limit the application of functional and structural testing to certain test levels only.