助动词用法讲解：助动词一般没有词意，不能单独作谓语动词。其作用在于帮助构成各种时态、语态、否定、疑问等。
1.助动词be(am, is, are, was, were, being, been)的用法
(1) be后跟现在分词构成进行时态。
Who is playing the violin?谁在拉小提琴?
She was reading a book then.那时她正在读书。
(2)be后跟过去分词构成被动语态。
He was asked to do the work.有人要他干这件工作。
You are invited to attend the meetintg.有人邀请你参加会议。
(3)be 后跟不定式作谓语，有如下几种情况：
①表示计划、安排将要发生的事。
Who are we to meet?我们要见谁呀?
I'm to have supper with John this afternoon.今天下午我要与约翰一起吃晚饭。
②表示指示、命令，否定式表禁止。
You are to see the headmaster today.今天你必须去见校长。
You are not to enter the room without permission.未经允许你不能进入房间。
③表示义务、责任等，同should。You are to be back before 5.你得在5点钟以前回来。
What is to be done?该干什么。
④表示可能性，与情态动词may, can同义。
Such books are to be found in any library.这种书任何图书馆都有。
Not a sound was to be heard.一点声响也没有。
⑤表示后来发生的事，可以用来表示命运或注定
They say good-bye, little knowing that they were never to meet again.他们告别了，没想到再也不能相见了。He was to regret the decision.他有一天会后悔做出这一决定的。
⑥用于习语
Where am I to go? 我该向何处去?
What am I to do? 我该怎么办?
2.助动词have(has, had, having)的用法
(1)助动词have可以构成完成时或完成进行时
He has been a doctor for 10 years.他当医生十年了。This is the place I have been longing to visit.这就是我一直渴望参观的地方。
(2)和不定式构成谓语，表示客观上不得不做的事情。We've missed the train. We'll have to wait for another one.我们己经误了火车，我们只能等下一列。
-Do we have to start work?我们得立刻工作吗?
-No. We don't have to.不，不必了。
3.do(does, did) 的用法
(1)构成疑问句或否定句
How did you know about it?你是怎样知道这件事的。He does not smoke. 他不抽烟。
(2)加强语气。
He did tell that.他的确告诉了此事。
Do come and see us.一定来看我们。
(3)代替前面刚出现的动词，避免重复。
-You like popular music, don't you?你喜欢流行音乐，是吧?
-Yes , I do.是的，我喜欢。
He speaks French as fluently as she does.他讲法语和她讲的一样流利。
(4)用于倒装句中。
Never did he pay attention to my words.他从不注意我的话。
Only then did I understand the importance of English.只是那时，我才了解到英语的重要性。
(5)构成否定的祈使句。
Don't be so careless.不要那么粗心。
Do not hesitate to come for help.只管来求助。
4.shall(should)和will(would) 的用法
(1)shall(should)用于第一人称的将来时中
I shall think it over.我要好好考虑一下。
When shall I see you again?我何时再见到你?
I rang up to tell her that I should leave for London. 我打电话告诉她我要去伦敦。
(2)will用于第二、第三人称的将来时态中，在现代英语中可以用于所有人称
He will be 30 next month. 他下月将是30岁。
You will have an English test tomorrow.明天你有英语小测验。
He wanted to know when you would finish the writing.他想知道你何时完成写作。
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