We first met on a train in 2000. We both felt immediately that we each other for years.

问题补充：

We first met on a train in 2000. We both felt immediately that we each other for years.

A. knew

B. have known

C. had known

D. know

答案：

A. knew

B. have known

(答案→)C. had known

D. know

解析：.

C。根据主句中的felt可知，其后的宾语从句应用过去时态，故可排除B和D；再根据语境和句中的for years可知用过去完成时比用一般过去时更佳。