Загадай вопрос к подчёркнутому слову.

They were in the forest last week

Вообще-то, с 'they' употребляется 'were'. У вас ошибка.

 Выбирайте нужное слово:Who were in the forest last week? (they)Where were they last week? (in the forest)When were they in the forest? (last week)What did they do in the forest last week? (were)