=>
Ex2/
1. did
2. Did/go
3. visited
4. didn't help
5. were not
6. did/design 
7. didn't crash
8. took off
9. Did/phone
10. didn't drink

Ex3/
1. arrested
2.  went/has come
3. has already bought
4. has your team won
5. Did you visit/stayed
6. Have you done/finished
7. was
8. have not seen/arrived
9. got/has had
10. didn't write/have worked

Ex4/
1. played
2. have cleaned/repaired
3. went
4. have read
5. met
6. have never visited
7. bought
8. have not done
9. Have you ever played
10. have not eaten
Ex5/
1. have lost
2. arrived
3. has broken
4. has lived
5. left
6. stayed
7. has always written
8. did
9. Has/phoned
10. thiếu từ trong ngoặc

Ex6/
1. have learned
2. visited
3. cycled
4. have never tried
5. Have you found
6. have known
7. listened/went
8. has been
9. has baked