We first met on a train in but we both felt immediately that we each other for year

问题补充：

We first met on a train in ，but 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：

根据题干所提供的信息，首先弄清说话者在谈论过去的事情，因此用过去时，排除B、D两项，然后考虑动词know在felt之前，即过去的过去，因此用过去完成时。