虚拟语气

if 的虚拟

	主句	从句
现在	were/did	would do
过去	had done	would have done
将来	were to do/should do	would do

would可替换为should might could

 

主句用“要求，命令，建议”等从句动词用（should）do 或被动 （should）be done