1) a) have
2) a) Have you worked all day?
3) c) was working
4) c) since
5) a) much
6) b) has not he
7) c) anybody
8) b) said
9) b) told
10) b) had
11) c) is repairing
12) a) yet
13) a) a few
14) a) saw
15) c) has not made
16) c) have passed
17) b) was caught
18) a) to open
19) a) to study
20) a) passing
21) b) will see