Mark the letter A, B, C or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions
It was only when Mr Hoan announced the result did he know that he was the winner of the contest
A. only when
B. announced
C. did he know
D. was
Đáp án : C
Cấu trúc câu chẻ với chủ ngữ giả: It + be + only when + mệnh đề + that + mệnh đề = chỉ khi… thì ai mới làm gì. Muốn đảo ngữ thì phải dùng: Only when + mệnh đề + did + S + V không chia -> Sửa C: that he knew