we didn’t know each other but now we are good friends.A. FirstB. First of allC. At firs

问题补充：

, we didn’t know each other, but now we are good friends.

A. First

B. First of all

C. At first

D. For the first time

答案：

A. First

B. First of all

(答案→)C. At first

D. For the first time

解析：A. First第一； B. First of all首先； C. At first 起先；D. For the first time第一次。结合下句但是现在我们是好朋友了可知上句是起先我们彼此不认识。故选C。