题目内容：

the ground isn't wet,it -----last night A can't have rained B couldn't have rained C couldn't rain
为啥

优质解答

选B.
couldn't have done 表示对过去的一种否定推测,意思是：过去不可能怎样.
首先排除C,因为要用完成时态,表示过去对现在造成的影响.
其次排除A,因为对过去的推测,要含有过去时.