求what if 的用法和例句。

求what if 的用法和例句。

一、如果what if是对现在情况的表达，不用虚拟语气，就用一般现在时【你的例句一】
二、如果what if后面是对过去、将来的推测、假设，需要用虚拟语气
1、如果表示对将来的推测 有这几种用法：
①if+主语+were to do
②if+主语+should/would/could/might+do
③if+主语+did（动词过去式）/were （be动词都变were） 【你的后三个例句都是这种用法】
2、对过去事实的推测
If+主语+had done（过去完成时） →what If I had got a better job？追问方便解释一下，虚拟语气吗追答Subjunctive Mood (虚拟语气)
非真实条件句的虚拟：(if从句比正常情况提前一个时态)
(Ls. 15-16) It wouldn't be so bad if he’d let a taxman work on the forms with him, but he insists on doing it himself…
与现在事实相反： if用过去式或用should/were to 表示更小的可能性，主句用should/would/could/might＋不定式。
I would have thought they were city fellows if I hadn’t seen the flying saucer stepped in.
与过去事实相反： if用过去完成式（had+done），主句用should/would/could/might+have done (完成体)追问请多给我一点what if 的例句。追答what happens if there is not any water in the earth.
如果地球上没有水了怎么办？What happens if Tom doesn't pass the exam?汤姆如果考试不及格，会怎么样？

祝你进步v追问what if 主语 should 的例句有吗?