=>
15. C if I knew/who he was
16. C if she was planning
17. A whether I was doing
18. B there (câu tường thuật here -> there)
19. B were/would travel
20. A the previous day ( yesterday -> the previous day)
21. A asked sb not to V : yêu cầu ai không làm gì
22. C (yesterday -> the day before/the previous day)
23. B (tomorrow -> the following day)
24.B hadn't met/had left
25. B whwether the children could
26. C was walking
27. C she hadn't taken
Câu tường thuật dạng Yes/No questions : asked sb if/whether S V(lùi thì)
Câu tường thuật dạng Wh - questions : asked sb + từ để hỏi + S V(lùi thì)
Lùi thì trong câu tường thuật : (riêng câu đk loại 2 -> không đổi)
HTĐ -> QKĐ
HTTD -> QKTD
HTHT -> QKHT
QKĐ -> QKHT
Will -> Would
Can -> Could