题目：有些假设别当真，那是虚拟语气
【知识点1 — if条件状语从句】
一般是if引导的从句在前面，主句在后面，中间用逗号隔开。从句比主句提前发生，也就是提前一个时态。
【知识点2 — 虚拟语气】
假设的情况与事实相反，或者可能根本实现不了，这时候不能用一般的if条件语句，需要使用虚拟假设，来为我们创造这种理论上不可能的条件。
【知识点3 — 和现在事实相反的虚拟语气】
时态往过去推一级
从句：if+主语+谓语用过去式（be通常用were）
主句：主语+谓语用“would+动词原形”
示例：
If I were you,I would change my lifestyle.
练习：
If I was rude to you,then I am sorry(我可能确实没有礼貌)
If I were invisible,I would walk into pop concerns for free.(我实际上不能隐身)
【知识点1 — 一般条件句VS虚拟条件句】
If I have time,I will go for a walk.如果我有时间就会去散步
If I had time,I would go for a walk..如果我有时间就会去散步(可惜我没有时间去散步)
示例：
虚拟语气建议：
If I were you,I would choose the bright one.
虚拟语气提醒他人:
If I were you,I wouldn't drag its tail.It may bite you.
【知识点2 — 和现在事实相反的虚拟语气】
从句：If + 主语 + 谓语用过去式（be通常用were）
主句：主语 + 谓语用should（would,could,might）+动词原形
拓展：
主句中用would强调结果，could强调能力，might强调可能性
示例：
If you tried again,you would succeed.如果你再试一次，就成功了。
If you tried again,you could succeed.如果你再试一次，就能成功了。
If you tried again,you might succeed.如果你再试一次，就可能成功了。
If I knew her number,I could ring her up.
【知识点3 — 和过去事实相反的虚拟语气】
从句：主语+谓语用过去完成时（had+过去分词）
主句：主语+谓语用should（would，could，might）+ have + 过去分词
示例：
If I had left sooner,I would have been on time.(其实我没有早出发，而且已经迟到了)
If I had studied as hard as him,I could have gotten an A+.
【知识点4— 和将来事实相反的虚拟语气】
从句：主语 + 谓语动词用：
1.过去式（be通常用were）
2.should do（可能性很小，“万一”）
3.were to do（计划实现不了）
主句：主语 + 谓语用should（would，could，might+动词原形）
示例：
If it rained tomorrow,the basketball match would be put off.【其实可能不会下雨，篮球赛也不会推迟】
If it should rain tomorrow,the basketball match would be put off.【其实下雨的可能性很小很小，篮球赛也不会推迟】
if I should fail the exam,I would try again.万一这次考不过，就要二刷。
拓展：
和将来的事实相反的虚拟语气，其实假设并不一定会跟事实相反，它只是一种推测。如果If从句中谓语动词用的是过去式，表示不确定这个动作发生的可能性是多少。
和将来事实相反的虚拟语气，If从句中用were to do something,代表说话人不鼓励这么做，可以理解为警告。
示例：
If you were to say another word,she would kick your ass.你要是再废话，她（你妈）就要揍你咯。
If you were to break the law,you would be sent to prison.
