we ( ) the difficulty together,but why didn't you tell me?

问题描述:

we ( ) the difficulty together,but why didn't you tell me?
A.could face B.might face C.could have faced D.must have faced
为什么选C不选B

could have done的格式是表示对过去的推测
从 why didn't you tell me看出,这正是对过去的推测
而might还是对现在的推测,虽然用过去式的样子,但是不是过去式,只是语气的委婉