1. Mary has lost her hat and she has been looking for it until now. 

2. I have read the novel written by Jack London several times before. (có "several times before" nên chia theo thì HTHT)

3. He has written a book since last year. (có "since last year" nên chia theo thì HTHT)

4. How long have Bob and Mary been married? ("How long" là câu hỏi dùng với thì HTHT)

5. When the police arrived, the car was going.

6. While we were doing a sightseeing tour, our friends lay on the beach.

7. They had eaten everything by the time they arrived at the party. (QKHT + by the time + QKĐ)

8. While Tom was playing the piano, his mother did the washing-up.

9. I went after they had finished their work. (chia theo thì QKHT)

10. The light went out while I was having dinner.

Câu 5, 6, 8, 10 đều là diễn tả 1 hành động đang diễn ra trong quá khứ thì có 1 hành động khác xảy ra xen vào nên phải chia theo thì QKTD

#NOCOPY

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