1.He will repair your watch (Who)
2.Your watch will be repaired (What)
3.He can repair your watch (Who)
4.Your watch can be repaired (What)
5.They must test this new car (Who)
6.This new car must be tested (What)
7.You have to write this letter again (Who)
8.This letter has to be written again (What)
9.I told you he could do it (Who)
10.I told you it could be done (What)
11.I told you he would do it (Who)
12.I told you it would be done (What)
13.I can not find my bag.Someone has stolen it (Who)
14.I can not find my bag.It has been stolen (What)
15.I can not find my bag.Someone must have stolen it (Who)
16.I can not find my bag.It must have been stolen (What)