— I didn’t know you were friends with Mr. Smith. — We each other for6 years.A. knewB. are

问题补充：

— I didn’t know you were friends with Mr. Smith.

— We each other for6 years.

A. knew

B. are known

C. have known

D. will know

答案：

A. knew

B. are known

(答案→)C. have known

D. will know

解析：句意：我不知道你和史密斯先生是朋友。——我们已经彼此认识六年了。结合语境可知本句描述的是现在已经完成的动作。故选C。