Give the correct form of the verbs in the past perfect tense.
1. He couldn’t open the door because he (lose) ____________________ his key.
2. They (go) _________________ to bed when I arrived.
3. My friends (leave) _____________ by 10.00.
4. Peter was angry because Kikki (take) _____________ his CD.
5. The film (finish) ____________________ by 8.00