___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?

___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?
___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?

___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?
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

不是过去完成时，是一般过去时，相当于if they had time ,..

不是过去完成时，had 是Have的过去式，实意动词“有”

虚拟倒装，与将来相反，条件句用过去时，主句用would do
不是过去完成时，是一般过去时，相当于if they had time