To combat HIV infection, you could target: viral fusion with the plasma membrane of a host cell, reverse transcriptase action, integration of the viral genome into the host genome. The second option is probably most likely to succeed.
Work Step by Step
See Fig. 19.8 and imagine where the steps could be blocked to stop infection. As an analogy, think of the host cell as a castle and then identify analogous things in invasion of a castle (viral fusion with the plasma membrane is like breaching the castle wall). Then ask yourself if such a thing could be stopped.