用所给动词的适当形式填空。
1. By the end of last year, the famous writer _____ (write) 20 books.
2. When we _____ (get) to the cinema, the film _____ (on) for half an hour.
3. Before he _____ (come) here, he _____ (live) in Britain for ten years.
4. By the time I _____ (arrive), she _____ (leave).
5. I _____ (learn) a lot of English songs before I _____ (be) ten.
