语法:情态动词 should/ought to/ had better
◆ should和ought to
1. should 作为情态动词,没有人称和数的变化。通常用来表示现在或将来的责任或义务,译作“应该”、“应当”,这时它可以和 ought to 互换使用。例如:
should /shouldn’t
I/You/He/She/We/They + discuss it.
ought to /ought not to 炒期货是什么意思
You should /ought to complete your test in time.
你们应该按时做完你们的实验。
一般疑问句及回答: --- Should we discuss it now? --- Yes, we should/ ought to.
--- Ought we to discuss it now? --- No, we shouldn’t/ ought not to.
Eg: We ought to be more careful with our homework.
They should finish the work on time.
He ought not to do it at once.
2. ought to/ should区别
should如胶如漆谈的是自己的主观看法,
ought to则更多反映客观情况,在谈到法律、义务和规定时使用。
Eg: We should/ought to help each other and learn from each other in our work.
She is your mother, so you ought to support her.
We ought to go and e Mary tomorrow, but I don’t think we will.
◆ had better
为固定搭配,无人称,数和时态的变化,用来表示给予建议,后面接动词原形,had better
通报格式 do sth意为“最好干某事…”
Eg: You had better be on time for your lessons. 你最好准时上课。
had better 通常缩写成’d better
Eg: You had better be careful when you cross the street.= You’d better be careful when you
cross the street. 当你过马路的时候,你最好小心点
肯定形式:had better do sth最好干某事
否定形式: had better not do sth最好不要干某事女孩英语单词
Eg: You had better go and e a doctor. 你最好去看下医生。
He had better not go out now. 他最好现在不要出去。
含有 had better的反义疑问句,把had作为助动词, 否定用 hadn’t。
Eg: We’d better stay at home today, hadn’t we? 我们最好是呆在家里,是吗?
She had better get ready for the coming exam, ?
其他情态动词复习
◆ can(could)与be able to
can=be able to 朝代顺序能够,表示能力
区别:
can只有两种时态, 即can 和could
be able to 有多种时态, 如was/were able to, will be able to, have/has been able to等
表示过去通过努力终于做成了某事要用be able to,而不能用can。
Eg上善若水图片: I was able to swim to the bank after the boat turned over.
can能表否定猜测,be able to不能。can的这种用法主要用于疑问句和否定句。
Eg:Somebody is knocking at the door. Who can it be?
It can’t be our teacher who is knocking at the door.
其肯定形式是must be。如: It must be our teacher who is knocking at the door.
◆ have to和must
'必须' have to 表示客观的必须,
must 表示主观的必须
My brother was very ill, so I had to call the doctor in the middle of the night. 我弟弟病得很厉
害,我只得半夜里把医生请来。(客观上需要做这件事)
He said that they must work hard. 他说他们必须努力工作。(主观上要做这件事)
have to有人称、数、时态的变化(has to/had to)
must只有一种形式。He had to look after his sister yesterday.
否定结构: don't have to 表示"不必"
mustn't 表示"禁止",
You don't have to tell him about it. 你不一定要把此事告诉他。
You mustn't tell him about it. 你一定不要把这件事告诉他
[注]:回答must提出的问题
Eg:---Must I do it now?
---Yes, you must. / No, you needn't.
◆ may 和 might
表示推测,意思是:可能,可用于肯定与否定推测。
It may rain this evening. You'd better take an umbrella. 今晚可能要下雨,你最好带上雨伞。 纽扣英语
may过去式为might
◆ need
做实义动词 需要 need to do sth 否定形式:don’t need to do sth
做情态动词 需要 need do sth 否定形式:needn’t do sth
Eg: You need finish / need to finish your homework today.
[注]:need/must 提问,回答需要注意:
Need I do my homework now? --Yes, you must(你必须)./ No, you needn’t/you don't have to(你不必).
Must I finish my homework now?--Yes, you must(你必须)./ No, you needn’t/you don't have to(你不必).
课堂作业
一、单项选择。
( ) 1. John_____ come to e us tonight, but he isn't very sure yet.
A. may B. can C. has to D. must
( ) 2. They _____ do well in the exam.
pr域名 A. can be able to B. be able to C. can able to D. are able to
( ) 3. --May I take this book out? --No, you_____.
A. can't B. may not C. needn't D. aren't
( ) 4. You_____ go and e a doctor at once becau you're got a fever.
A. can B. must C. dare D. would
( ) 5. --Can you speak Japane? --No, I______.
A. mustn't B. can't C. needn't D. may not
( ) 6. --He______ be in the classroom, I think.
--No, he ______ be in the classroom. I saw him go home a minute ago.
A. can; may not B. must; may not C. may; can't D. may; mustn't
( ) 7. --Shall I get one more cake for you, Dad?
--Thanks, but you______, I've had enough.
A. may not B. must not C. can't D. needn't
( ) 8. Even the top students in our class can't work out this problem, so it _be very difficult.
A. may B. must C. can D. need