关于虚拟语气的疑问：虚拟语气有主从句之分，让我很困惑的不含if的虚拟语气。

Question

。。。as if/as though+主语+虚拟语气过去式/虚拟语气过去完成时，
If only+主语+虚拟语气过去式/虚拟语气过去完成时，
什么情况下用主句格式，什么情况下用从句格式？极度糊涂中。。。。。
答的好加分！

Answer 1

as if / though 引导的虚拟语气，虚拟只是在从句中使用，主句中不用虚拟， 与现在事实相反用过去时，与过去事实相反用过去完成时。如果是所述的是真实的，就用直陈语气。
eg ,It sounds as if it is raining． 听起来像是在下雨。 （直陈语气）
You look as if you didn’t care． 你看上去好像并不在乎 （ 与现在事实相反）
He talks about Rome as if he had been there before． 他说起罗马来好像他以前去过罗马似的（与过去事实相反的虚拟语气。
If 条件句中的虚拟要分主句和从句，
从句与将来，现在和过去事实相反用
If 主语+ were to do/were / did / had done
而 主句 表示与将来，现在和过去事实相反，主句应该是
主语 + would /could/might + do /have done .
eg .If I were you , I would not do it .
If he had driven carefully enough , the accident would not have happened.
If only 是从句， 虚拟就和If 条件句相同。
If only hadn't done that !