Complete the question: Who had Stacy () before she returned last night?

• A. Been visiting
• B. Visiting
• C. Was visiting
• D. Had visited

Answer: (A)

This question tests using the past perfect continuous to describe an ongoing action that happened before another past event. To show that Stacy was in the middle of visiting someone up until the moment she returned last night, we need the form had been visiting. The full sentence becomes: Who had Stacy been visiting before she returned last night? The structure uses had as the auxiliary for the past perfect, been as the participle, and visiting in the -ing form to signal ongoing action up to that past moment.

Why the other options don’t fit as well: dropping the auxiliary and using been visiting isn’t correct because the sentence needs the past perfect to link to the later past event. Using visiting alone isn’t grammatical in this context. Was visiting describes a past continuous action at a specific time, not necessarily the duration up to the return. Had visited is past perfect simple and indicates a completed action, not one that continued up to the return.