假设类型条件从句谓语动词形式主句谓语动词形式与现在事实相反动词过去时(be用were)Should(would,could,might) 动词原形与过去事实相反Had 过去分词Should(would,could, might) have 过去分词与将来事实可能相反动词过去时(should 动词原形,were to 动词原形)Should(would,could,might) 动词原形
If there were no gravity, we should not be able to walk.假如没有引力,我们就不可能行走。
I wouldn’t have known what these were for if I hadn’t been told.假如别人不告诉我,我就不知道这些东西是干什么的了。