10. What were you doing . . .
11 had been teaching
12. have you been doing. . .
13 have read
14. have you seen
15. I shall be sleeping. . .
16. Have you found. . .
I'm still looking for it.
I have already been looking for it for two hours but I haven't found it yet.
17. have been sailing. . .
18. have been waiting
19. had been writing
would finish
20. found. .
had got up and were waiting for him.