Identify the one underlined word or phrase....

Câu hỏi: Identify the one underlined word or phrase. A, B, C or D - that must be changed for the sentence to be correct. If Monique had not (A) attended the party, she never would meet (B) her old friend Dan, whom (C)  she had not seen (D) in years.

A. Had not

B. Never would meet

C. Whom

D. Had not seen