be动词，情态动词，助动词do/does的用法区别及练习助动词，顾名思义就是帮助动词完成疑问及否定的，本身没有什么含义。
主要的助动词有be,do,will,have等，其用法详述如下：一、⑴由连系动词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?(2)was 是am,is的过去式，were是are的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。
二、(1) 由情态动词can, may,will ，shall等构成的句子: 变一般疑问句时把can, may,will ，shall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?（2）could,might,would,should是can,may,will,shall的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。
三、（1）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?（2）did是do和did的过去式，变一般疑问句时把did放在句子前面. 变否定句时把didn’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都要变回原型。
四、(1)由have,has构成的现在完成时句子，变一般疑问句时把have,has提到句子的前面，句尾用问号即可。
变否定句时直接在have,has后面加not即可。
例如：肯定句：He has read today’s newspaper.一般疑问句: Has he read today’s newspaper.?否定句: He has not read today’s newspape画线提问: 对he提问: Who has read today’s newspaper?对today’s newspaper提问: What has he did?(2)had是have和has的过去式，在构成的过去完成时句子中，变一般疑问句时把had提到到句子的前面，句尾用问号即可。
变否定句时直接在had后面加not即可。
(3)若have,has,had没有出现在完成时的句子中，则当实义动词对待，请参考实义动词的用法。
五、第一人称I，we在变疑问句时，应变为第二人称you。
“I am, you /we /they are”这是初一最简单的固定搭配，不应再唠叨了吧！六、is,has,does用于第三人称的现在时态，was用于第三人称的过去时态。
针对性练习按要求改写句子：1.I have been to Beijin(一般疑问句)______ ______ __________ to Beijin?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 were s ome flowers on the teachers’ desk.(一般疑问句)______ ______ ______ flowers on the teachers’ desk?5.There were 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.They had lunch(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 has already written the letter.(改为否定句)she____ _____13.She was 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 got up at six yesterday(对划线部分提问)______ ______ __________ you get up yesterday?16.They liked 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. (就划线部分提问)_______ ______ _______ ______ ______ _______plant __________?21.Miss Li goes to Hong Kong by plane.（同义句）Miss Li ________ _________ Hong Kong.22. The women worked 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。