题目内容：

___time,they would certainly come and help to do the work.
这里答案用had they
这是一句虚拟的倒装句,但would certainly come and help 是一般现在时,那么从句要用过去时,为什么从句用过去完成时?

优质解答

Had they在这里等于if they had ,这里had 是的意思,they had time ,不是过去完成时