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 ...方便解释一下，虚拟语气吗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)请多给我一点what if 的例句。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vwhat if 主语 should 的例句有吗?