6. Their best performance has been finished.
Bị động hiện tại hoàn thành.
7. It is useless to complain about that matter.
It's adj + to V + O
8. Peter hasn't come here since 2005.
The last time + S + V-ed + ... + was + thời gian = S + have/has + not + part participate + ... + since/for + thời gian.
9. If we don't take a taxi, we won't get there on time.
Câu điều kiện loại 1 (chứa unless = if ... not)
50. The man who was accused of stealing the money refused to answer the police’s enquiries.
Đại từ quan hệ who.