Question

I went to Rebecca's house, but she wasn't at home. She____out
left
was looking
had gone
were tidying
had forgotten
had left
went

Answer 1

I went to Rebecca's house, but she wasn't at home. She had gone out

Тоже самое что и в прошлом, тут действие произошло до действия в прошедшем, то есть используем past perfect:

had gone

had forgotten

had left

Из этих трех лучше всего подходит: had gone