13. His parents complained about his absence from school. It's wrong of him not to tell them about that.
A. He should have told his parents about his absence from school.
B. He might have told his parents about his absence from school.
C. He must have told his parents about his absence from school.
D. He can have told his parents about his absence from school.

Loại D vì sai cấu trúc.

Loại B, C vì không mang nghĩa phỏng đoán.

`to` A.

14. I'm sure that she didn't kill him because she was with me at the supermarket when the murder happened.
A. She mustn't have killed him because she was with me at the supermarket when the murder happened.
B. She needn't have killed him because she was with me at the supermarket when the murder happened.
C. She can't have killed him because she was with me at the supermarket when the murder happened.
D. She shouldn't have killed him because she was with me at the supermarket when the murder happened

Loại A vì sai cấu trúc.

Loại B, D vì sai nghĩa với đề.

`to` C.
15. Perhaps he will return before you call.
A. He may be returning before you called.
B. He may/might have returned before you called.
C. He should have returned before you called.
D. He may return before you call.

Loại A vì sai cấu trúc.

Loại C vì should have Vp2: diễn tả sự việc lẽ ra xay ra ra trong quá khứ mà không.

Loại D vì must have Vp2: diễn tả suy đoán hợp lí trong quá khứ vì có cơ sở rõ ràng.

Mà vì perhaps = may/ might `to` B.
16. You don't need to type the letter right now. You can do it later.
A. You mustn't type the letter right now because you can do it later.

B. You can't have typed the letter right now because you can do it later.
C. You needn't type the letter right now because you can do it later.

D. You needn't have typed the letter right now because you can do it later.

Giải thích: 

mustn't V: diễn tả sự cấm đoán, không được phép làm gì

can't have Vpp: diễn tả dự đoán về một việc không xảy ra trong quá khứ

needn't V: không nhất thiết phải làm gì

needn't have Vpp: diễn tả về một việc lẽ ra không cần làm trong quá khứ, nhưng đã làm

`to` Câu đề: Bạn không cần phải gõ lại bức thư ngay bây giờ. Bạn có thể làm điều đó sau. Vì thế ta sẽ dùng needn't V.

Dịch: Bạn không nhất thiết phải gõ lại bức thư ngay bây giờ vì bạn có thể làm sau.

`to` C.

13. His parents complained about his absence from school. It's wrong of him not to tell them about that.
A. He should have told his parents about his absence from school.

vì tất cả bị sai cấu trúc và nghĩa ko liên quan tới đề.

14. I'm sure that she didn't kill him because she was with me at the supermarket when the murder happened.
C. She can't have killed him because she was with me at the supermarket when the murder happened.

vì mấy cấu khác bị sai câu trúc và nghĩa.
15. Perhaps he will return before you call.
B. He may/might have returned before you called.

vì perhaps = may/ might nên ta chọn B.
16. You don't need to type the letter right now. You can do it later.
C. You needn't type the letter right now because you can do it later.

Bạn có thể làm điều đó sau. Bạn không cần phải nhập chữ cái ngay bây giờ vì bạn có thể làm điều đó sau.

Bạn không cần phải nhập chữ cái ngay bây giờ.