During the implementation phase, the quality assurance team will typically create specific test cases. This activity involves writing detailed scenarios and steps that will be used to verify that the system behaves as expected and meets the defined requirements.
The other options listed, such as drafting a defect report, revising the test plan, and developing a test plan, are activities that may occur at different stages of the software development lifecycle but are not typically primary tasks during the implementation phase. So the best answer here is:
create specific test cases.