Задание
Read these sentences and fill in the gaps with the correct verb form in the past perfect continuous.
Example 0. John __________ his dog all day. He was tired yesterday. (walk)
Answer 0. had been walking.
We [ ] to open the door for five minutes when Jane found her key. (try)
They [ ] for an hour before I went to bed. (sleep)
We [ ] in that college for five years. It was difficult. (study)