sat语法问题,不太明白虚拟语气应该怎么判断,能把几个固定搭配列出来就更好了

现在：主句：would do
从句：were/did
将来：主句：would do
从句：did/were to do
过去：主句：would have
从句：had done/been
背下来,做题的时候套就好了把.