1与现在事实相反,从句谓语用动词过去式（be动词一般用were）；主句用should(would,could,might) do
2与将来事实相反：从句谓语可用动词过去式,should do动词原形或者用were to do；主句谓语形式也是用should(would,could,might) do
3,与过去相反的事实,从句中用had done；主句谓语是由should(would,could,might) have done
虚拟条件句谓语用过去分词吗
1与现在事实相反,从句谓语用动词过去式（be动词一般用were）；主句用should(would,could,might) do
2与将来事实相反：从句谓语可用动词过去式,should do动词原形或者用were to do；主句谓语形式也是用should(would,could,might) do
3,与过去相反的事实,从句中用had done；主句谓语是由should(would,could,might) have done