Câu 11: have seen lots -> had seen lots
Câu 12: listen intently-> listening intently
Câu 13. change -> changed
Câu 14. is still-> was still
Câu 15. I'm shopping-> I was/were shopping
Câu 16. is having-> was having
Câu 17. are-> have been married
Câu 18. are believing-> believe
Câu 20. waking-> wakes
Câu 21. drives -> was driving
Câu 22. will certainly complete -> will have certainly completed
Câu 23. buys -> bought
Câu 24. We’ll be cycled -> We’ll be cycling
Câu 25. won’t come -> don’t come
Câu 26. was knocking -> knocked
Câu 27. didn’t drink -> hasn’t drunk