51.It’s been two years since I stopped doing competitive sports. → I haven’t _______________________________________________________. 52.I have never met such a beautiful girl before. → It ______________________________________________________________. 53.He has worked for this company for more than 15 years. → He started ________________________________________________________. 54. The train has left for one hour. → __________________________________________________________ ago. 55. I last saw Scott last Sunday. → I have ______________________________________________________________.

Cách làm:

1. Dùng cấu trúc "have/has + not + V3" để biến đổi câu.
2. Dùng cấu trúc "never + have/has + V3" để biến đổi câu.
3. Sử dụng cấu trúc "for more than + thời gian" để biến đổi câu.
4. Dùng cấu trúc "ago" để biến đổi câu.
5. Sử dụng cấu trúc "have/has + V3" và "last" để biến đổi câu.

Câu trả lời:
51. I haven’t done competitive sports for two years.
52. It is the first time I have met such a beautiful girl.
53. He started working for this company over 15 years ago.
54. The train left an hour ago.
55. I haven't seen Scott since last Sunday.

I have not seen Scott since last Sunday.

The train left one hour ago.

He started working for this company more than 15 years ago.

It is the first time I have met such a beautiful girl.