I heard they went skiing in the mountains last winter.

题目

I heard they went skiing in the mountains last winter.
A.may not be B.won't be C.couldn't be D.mustn't be

答案

应该选C,因为从时态来看 “last winter”是过去时态,这句话是过去时态的虚拟语气,动词形式应该用过去时,所以选择C.从另一个角度讲,这句话的陈述句是“I heard they must be went skiing in the mountains last winte...