D. Put the verbs into the past simple, past continuous, past perfect or past perfect continuous.

17. We didn’t see Jane at the party, because when we came she had already gone home. 18. She was cooking dinner when I rang her yesterday. 19. Mark did not call me yesterday, but I hope he will call today. 20. Mary had been waiting for Kate for 30 minutes before she arrived. 21. When did James graduate from university?