Question

She _ (clean) the room before the guest came

Answer 1

Answer:

Cleaned the room before

Answer 2

Answer:

She had cleaned the room before the guest came.

The cleaning was done prior to the arrival of the guests. So we're talking about something that happened before another past event. Hence, the first event(had cleaned) should be in past perfect tense and the second event(came) should be in simple past tense.

Hope this helps you.