情态动词，be动词，助动词有什么区别

be动词，情态动词，助动词do/does的用法区别及练习
1. 由连系am，is，are构成的句子：变一般疑问句时把am，is，are提到句子的前面，句尾用问号即可。变否定句时直接在am，is，are后面加not即可。例如：
肯定句:He is a student.
一般疑问句: Is he a student?
否定句: He is not a student.
画线提问: 对he提问: Who is a student?
对 a student 提问: What is he? or What does he do?

2. 由情态动词can, may, should等构成的句子: 变一般疑问句时把can,may,提到句子的前面,句尾用问号即可.变否定句时直接在can,may,后面加not即可. 例如:
肯定句: She can swim.
一般疑问句: Can she swim?
否定句: She can not swim.
画线提问: 对she提问: Who can swim?
对swim提问: What can she do?

3. 由行为动词构成的句子: 需要加助词do或does. 变一般疑问句时把do/does放在句子前面. 变否定句时把don’t/doesn’t放在动词的前面。要注意观察动词的形式并对号入座。一般疑问句和否定句的动词三单式都要变回原型。
play-----do plays-----does

例如:
肯定句: They play football after school. He plays football after school.
一般疑问句: Do they play football after school? Does he play football after school?
否定句: They don't (do not) play football after school. He doesn’t’ play football after school.
画线提问: 对they/he提问: Who plays football after school?
对play football提问: What do they do after school? What does he do after school?
对after school提问: When do they play football? When does he play football?

针对性练习
按要求改写句子：
1.I know the answer.(一般疑问句)
______ ______ __________the answer?
2.We can see some birds.(一般疑问句)
______ ______ see ______ birds?
3.He designs clothes.(一般疑问句)
______ he ________ clothes?
4.There are some flowers on the teachers’ desk.(一般疑问句)
______ ______ ______ flowers on the teachers’ desk?
5.There are some apples on the tree.(否定句)
There ______ ______ ______ apples on the tree.
6.I think he is very old.(否定句)
I ______ think he ______ very old.
7.Please colour it green.(否定句)
______ ______ colour it green.
8.These doctors are helpful.(变否定句)
______ _______ ______ __________.
9.You may have some hot dogs.(一般疑问句)
_______ ______ ______ ______ ________?.
10.There aren’t any pears in the box.(同义句)
There are ______ pears in the box.
11.This sign means “No smoking”.
What ______ this sign _________?
12.She looks young. （改一般疑问句）
________ she _______ young?
13.She is young.（改为一般疑问句）
______ ______ ____________?
14.My pencils are in the pencil-box.(对划线部分提问)
______ ______ your pencils?
15.I get up at six every day.(对划线部分提问)
______ ______ __________ you get up every day?
16.They like to walk home.(改为一般疑问句)
______ they ________ _______ _______ _________?
17.These are cars.(用buses改写成选择疑问句)
Are these cars______ ______ ?
18.My plant is one month old.(就划线部分提问)
_______ ______ ______ _______ plant?
19.Two boys are in our house.(改为there be句型)
______ ______ two boys in our house.
20.My plant has two green leaves.
_______ ______ _______ ______ ______ _______plant __________?
21.Miss Li goes to Hong Kong by plane.（同义句）
Miss Li ________ _________ Hong Kong.
22. The women work in the shoe factory.（就划线部分提问）
_______ _______ ______ women __________?
23.He is happy, because he is going to take a trip tomorrow.（就划线部分提问）
_______ _______ ______ _________?
24.My father can cook the meals.（就划线部分提问）
_______ ________ ________ father __________?
25. You should add water often.（一般疑问句）
_______ ______ _______ water often?

一、变否定句时相关词的改变
肯定句变否定句时，除将谓语变为否定式外，句中其他词语也可能随之改变，如将some改为any，too和also改为either，already改为yet，and改为or等：
There are some birds in the tree. 树上有些鸟。
→There aren’t any birds in the tree. 树上没有鸟。
He likes the girl, too. 他也喜欢这个女孩。
→He doesn’t like the girl, either. 他也不喜欢这个女孩。
We have already seen the film. 我们已看过这部电影。
→We have not seen the film yet. 我们没有看这部电影。
He likes singing and dancing. 他喜欢唱歌和跳舞。
→He doesn’t like singing or dancing. 他不喜欢唱歌也不喜欢跳舞。
二、部分否定与完全否定
比较以下句子：
All of us laughed when we heard it. 听到这事时我们都笑了。(肯定句)
All of us didn’t laughed when we heard it. 听到这事时我们并未都笑。(部分否定)
Not all of us laughed when we heard it. 听到这事时我们并未都笑。(部分否定)
None of us laughed when we heard it. 听到这事时我们都没笑。(完全否定)
【注】可能涉及部分否定的词语有both, all, always, every等，即not both表示“并非两者都”，not all表示“并非所有的都”，not always 表示“并非总是”，not every表示“并非每个…都”。