This question tests the understanding of the past perfect tense, which is used to describe an action that was completed before another action in the past. The correct answer is B, as it correctly uses 'had finished' to indicate that the homework was completed before the movie started. Option A incorrectly uses the present perfect tense. Option C misplaces the past perfect tense, suggesting the movie started before the homework was finished. Option D uses the present tense, which is incorrect for describing past events.