He certainly revised the old lessons very carefully.   → He must………………………………………………………………….. He must have revised the old lessons very carefully.  Ta có : certainly = must have done...

Câu hỏi :

He certainly revised the old lessons very carefully.   → He must………………………………………………………………….. He must have revised the old lessons very carefully.  Ta có : certainly = must have done st (chắc chắn đã làm gì) – hai vế này mang nghĩa bằng nhau, đều chỉ sự chắc chắn