=>
1. D -> was going ( QKĐ when QKTD)
2. D -> thought
3. B -> visit ( every -> HTĐ)
4. A -> since ( HTHT since QKĐ)
5. A -> will have got married
6. C -> ask
7. B -> arrives
8. A -> has never told
9. B -> would ( câu tường thuật)
10. D when QKĐ, QKHT
11. C -> should stop ( nên dừng)
12. B -> has been ( up to now -> HTHT)
13.  B -> have been making ( HTHTTD)

14. D -> get
15. D -> had been (QKHT)
16. A -> has struggled
17. C -> did (said -> lùi thì)
18. C -> will be working ( at this time next week -> thì TLTD)
19. A -> have never seen 

1. (D) have gone ⇒ was going 

2. (D) will have thought ⇒ thought

3. (B) had visited ⇒ visit

4. (A) have studied ⇒ since

5. (A) has got married ⇒ will have got married

6. (C) will ask ⇒ ask

7. (B) will arrive  ⇒ arrives

8. (A) has ever told ⇒ has never told

9. (B) will ⇒ would 

10. (D) has already left ⇒ had already left 

11. (C) will stop ⇒ should stop

12. (B) had been ⇒ has been 

13. (B) are making ⇒ have been making 

14. (D) will get back ⇒ get back

15. (D) has been ⇒ had been 

16. (A) had struggled ⇒ has struggled

17. (C) do ⇒ did 

18. (C) was working ⇒ will be working 

19. (A) had naver seen ⇒ have never seen