16. did you watch
17. have already left
18.have you known
19.met
have known
20.happend

III
16. Did you watch the film E.T yesterday ?
17. They have already left the train station.
18. How long have you known Jonathan ?
19. I met him in 2009, so i have known him for 3 years.
20. What happened to Lucy last night ?
21. Did you read "Harry Potter" when you were on holidays ?

IV
1. I will stay here until he answers me.
2. She won't come until you are ready.
3. Miss Helen will help you as soon as she finishes that letter tomorrow.
4. Our English teacher is going to explain that lesson to us tomorrow.