as
as though什么情况下不是虚拟语气？
though什么情况下不是虚拟语气？
As though和as if表示，仿佛似乎好像,后面引导一个方式状语从句。如果从句所表示的内容是事实或者接近一个事实，那么就不用虚拟语气，用陈述语气。Everything was destroyed in the earthquake, it seems as though it was at an end.所有的一切都在地震中被摧毁了，看起来好像到了世界末日。
if引导的主句中有would一定是虚拟语态吗？
If从句中的would不一定都是虚拟语态。
If only you would help me next week, I would not be so nervous.
这里的If onlyIf。
从句里would是愿意的意思，是情态动词，不是虚拟语气的助动词。
而主句中的I would not be...中的would是虚拟语气助动词，不是愿意情态动词的意思。
if引导虚拟语气的用法？
1、表示与现在事实相反的情况：
从句：If 主语 动词一般过去时(Be动词用were)。
主句：主语 should/would/might/could do。
2、表示与过去事实相反的情况：
从句：If 主语 had done。
主句：主语 should/would/might/could have done。
3、表示与将来事实相反：
从句：①if 主语 were to do。
②if 主语 should do。
③if 主语 动词一般过去式（be动词用were）。
如何辨别虚拟语气中的三种时态？
1、对现在的虚拟结构：if 主语 动词动词过去时，主语 should/would 动词原形 ，should不可以省略。
【例句】If I had had enough money, I would have joined the swimming club.
【翻译】如果我有足够的钱，我就能去参加游泳俱乐部了。
2 、对过去的虚拟结构：if 主语 had 过去分词，主语 should/would have 动词过去时。
【例句】If she had told him about the danger, he would not have got hurt.
【翻译】如果她能早点告诉他危险，他就不会受伤了。
3 、对将来的虚拟结构：if 主语 should 动词原形（were to 动词原形），主语 would/should 动词原形，这个should 可以省略。
【例句】If he had followed my advice, he would not suffer so much now.
【翻译】如果他当初听我的意见，现在就不会受那么多的罪了。