二、简单句的核心变化

简单句的核心变化其实就是 一主一谓（n. + v.） 表达一件事情，谓语动词是其中最重要的部分，谓语动词的变化主要有四种：三态加一否（时态、语态、情态、否定），其中时态最重要。本章节讲解谓语动词情态的变化。

谓语动词的情态变化

1、情态：情绪和态度

对于每件事，人可以表达自己的情绪和态度，比如：你可以这样做、你不应该这样做。此时就可以使用情态来帮助表达
情态动词一般情况比较虚，一般情况不能单独使用，通常后面需要搭配一个动词原形来使用，即情态动词+动词原形
情态动词没有人称的变化
情态动词的时态变化有限只有现在时和过去时

现在时	过去时
must	无
can	could
will	would
shall	should
may	might

注：其中could、would、should、might有两个作用
①可以表示过去
②可以表示现在更委婉的语气
Can you help me？你能帮我吗？
Could you help me？please. 这里的could就表示你能不能帮我，很客气的语气.

情态动词变否定\疑问
无实义的动词直接加not变否定、直接提前变成疑问

原句	You can do it.
否定	You can not do it.
疑问	Can you do it？

Ⅰ、must

must 必须
We must finish the work within a week.
Air pollution must be taken seriously.

mustn’t 禁止，千万不要
You mustn’t do that. It’s wrong.

Ⅱ、can/could

can / could 能够，可以
The government can solve the problem of water pollution.
Tony could walk when he was only one year old.

Ⅲ、will/would

will/would 愿意/将要

will n.意愿

Will you marry me? 你愿意嫁给我吗？
l will travel abroad with my family.
Potential buyers would cheer for lower interest rates.

Ⅳ、may/might

may/might 可以、可能
To some extent, expressions may influence emotions.
Such bodily reaction might help moderate the work stress.
May I come in？
May I help you？

Ⅴ、should

should 应该
Students should work hard to pass the exams.
Those sick people should seek help from doctors.

2、每个情态动词都能表示推测

The details may be unknowable.
这个细节可以不被人所知。 细节是复数，应该用are，但因为使用了情态动词may，故后面接动词原形be。
Such searches must take years.
The loss of patience can potentially have a damaging impact on our professional and personal wellbeing.

3、情态动词 + have done/be doing

情态动词 + have done 强调完成时态，对之前的事情表示推测
情态动词 + be doing 强调对正在进行的事情表示推测

The way of saying those things may have led to misunderstanding.
或这些事情的方式，可能之前就导致了误解。

Now something similar could be happening in the South Africa.
现在相同的一些事情可能正在南美洲发生。

练习

1.In order to be a good salesclerk, you _____ (must not /will not) be rude to a customer.
为了成为一个优秀的推销员，你禁止 must not对顾客粗鲁

2.This pie is very good. You _____ (should /must) try a piece.
这个派非常好吃，你应该 should尝一块

3.Rice _____(should /must /may) have water in order to grow.
大米应该 should、必须 must需要水为了成长。
这俩个都可以，这就体现了英语是一门语言，选取的答案完全取决个人想要表达的含义

4.Don’ t be nervous. I think you _____ (can /must) make it.
别紧张，我相信你能 can做到

5.I am not sure. Probably he _____ (may /should)come later.
我不确定，他可能 may会晚点来

谓语动词：三态+一否（时态语态情态否定），通常都是混合当成一个整体出现的