Lesson3 Grammar
Tips：All things in their being are good for something.(天生我材必有用)
Learning aim: learn the use of the modal verbs have to /not have to , can/can’t, ought to /ought not to
Learning methods: observe----learn-----summarize------use
Learning steps:
StepI: Underline all the following words in the texts and translate them.
have to , don’t have to, ought to, ought not to, can’t,can
StepII: Match the verbs to their meanings.(A级)
1 have to a) not necessary
2 don’t have to b) necessary
3 can c) not allowed/not possible
4 can’t d) allowed/ possible
5 ought to e) not advisable
6 ought not to f) advisable
StepIII:Transtrate the following sentences.(B级)
1.1)I can’t go out now, I have to look after my baby .
______________________________________
2)I must find a job,my parents can’t support me any longer.
_____________________________________________
3)— Must we hand in our exercise books today?
— Yes, you must. (No, you don’t have to/need’t.)
________________________________________________
总结：must 和have to表示___________，但must表示___________观，have to表示_________观(如例句1，2所示)
读一读，记一记:
must与have to有下列几点不同：
① must表示的是说话人的主观看法，而have to则往往强调客观需要。
The play is not interesting. I really must go now.
I had to work when I was your age.
② must与have to 的时态差别： have有时态的变化,如三单has, 过去时had ,表示 客观上的不得不，能与所有 时态一起。must为情态动词, 无时态的变化 , 表示主观上的必须, 需要。
③ 二者的否定意义不大相同。如：
You mustn't go. 你可不要去。
You don't have to go. 你不必去。
④ 询问对方的意愿时应用must。如：
Must I clean all the room?
2 1)Can you speak English?
__________________________________________________ can表示能力(如体力和脑力方面)，意为“__________”等can表示能力时，还可用be able to代替。如：
I'll not be able to come this afternoon.
2)表示请求或允许，多用在口语中，意为“__________”等。
— Can/Could I go now?
— Yes, you can.(回答语中不能用could)
3) 表示惊异、怀疑、不相信的态度。(主要用在否定句、疑问句或惊叹句中)
Can this be true? ______________________
How can you be so careless! ___________________
This cannot be done by him. __________________
4)在变否定句时，直接在后加上“not”,可缩写成_________或___________, 但不能写成cann’t。例如：
(变成否定句) He can swim. → _______________________
3 ought意思是______________后面跟带有 to 的动词不定式否定式为_________________。(C级)
You ought to read these books if you want to know how to repair the motorcar.
____________________________________________
You ought to bring the child here.
_____________________________________________
You ought not to walk alone at night. _____________________________________________
注意： ought to和should的区别：
1.ought to语气略强。 2.should较常用。
3.ought to在美国英语中用的很少，而should却相当常用。
4.ought to属正式用语。
练一练：(C级)
1The man in the office____________be Mr. Black because he went home
just now.
A. mustn’t B. may not C. can’t D. needn’t
2---Can you go surfing with us this afternoon?
----I’d like to , but I ________ look after my sister at home , because my mother is ill.
A. need B. must C. have to D. should
3----Can I take this book out of the reading room?
