四、情態(tài)動(dòng)詞的基本用法
1、can / could
1）表示能力,could主要指過(guò)去時(shí)間.
Two eyes can see more than one.兩只眼比一只眼看得清.
Could the girl read before she went to school?這女孩上學(xué)前能識(shí)字嗎?
2）表示可能（理論上或是邏輯判斷上）.
The temperature can fall to –60℃,that is 60℃ below freezing.氣溫可降至—60℃,也就是零下60℃.
He can’t (couldn’t) have enough money for a new car.他不可能有足夠的錢買新車.
You mustn’t smoke while you’re walking around in the wood.You could start a fire.在林子里走時(shí)勿吸煙,那樣可能會(huì)引起火災(zāi).
3）表示允許.
Can I have a look at your new pen?我可以看一看你的新鋼筆嗎?
He asked whether he could take the book out of the reading—room.他問(wèn)他可不可以把書帶出閱覽室.
4）表驚異、懷疑、不相信等態(tài)度.主要用于否定句、疑問(wèn)句或感嘆句中.
Where can (could) they have gone to?他們會(huì)去哪兒了呢?
He can’t (couldn’t) be over sixty.他不可能超過(guò)六十歲.
How can you be so careless?你怎么這么粗心?
5）比較委婉客氣地提出問(wèn)題或陳述看法.
Can (Could) you lend me a hand?幫我一把好嗎?
I’m afraid we couldn’t give you an answer today.恐怕我們今天不能給你答復(fù).
2、may / might
1）表允許,might可以指過(guò)去時(shí)間,也可指現(xiàn)在時(shí)間,語(yǔ)氣更委婉.
You may take whatever you like.你喜歡什么就拿什么.
He told me that I might smoke in the room.他告訴我可以在房間里抽煙.
May (Might) I ask for a photo of your baby?我可以要一張你寶寶的照片嗎?
注意：在回答以may引起的問(wèn)句時(shí),多避免用這個(gè)詞,而用其它方式,以免顯得太嚴(yán)峻或不客氣.
如：Yes,please./ Certainly./ Please don’t ./ You’d better not./ No,you mustn’t.等,
2）表可能（事實(shí)上）.可以指過(guò)去時(shí)間,也可以指現(xiàn)在時(shí)間,但語(yǔ)氣更加不肯定.
He may be at home.他可能在家.
She may not know about it.她可能不知道這件事.
He was afraid they might not agree with him.他擔(dān)心他們可能不同意他的意見(jiàn).
They might be having a meeting,but I’m not sure.他們有可能在開(kāi)會(huì),不過(guò)我不肯定.
3、must
1）表示義務(wù).意為“必須”（主觀意志）.
We must do everything step by step.我們一切都必須循序漸進(jìn)地做.
You mustn’t talk to her like that.你不可能那樣對(duì)她說(shuō)話.
--Must we hand in our exercise—books now?我們現(xiàn)在就要交練習(xí)本嗎?
--No,you needn’t./ No,you don’t have to.不必.（這種情況下,一般不用mustn’t）
2）表示揣測(cè).意為“想必、準(zhǔn)是、一定”等,只用于肯定句.
He must be ill.He looks so pale.他準(zhǔn)是病了.他的臉色蒼白.
She’s wearing a diamond necklace.She must have a lot of money.她戴著鉆石項(xiàng)鏈,一定很有錢.
4.shall
1）表征詢意見(jiàn),用于第一、第三人稱疑問(wèn)句.
Shall I get you some tea?我給你點(diǎn)茶好嗎?
Shall the boy wait outside?讓那男孩在外面等嗎?
What shall we do this evening?我們今晚做什么?
2）表說(shuō)話人的意愿,有“命令、允諾、警告、決心”等意思,用于第二、第三人稱陳述句.
You shall do as I say.按我說(shuō)的做.（命令）
You shall have my answer tomorrow.你明天可以得到我的答復(fù).（允諾）
He shall be sorry for it one day,I tell you.有一天他會(huì)后悔的,我告訴你.（警告）
Nothing shall stop us from carrying out the plan.什么也不能阻止我們執(zhí)行這項(xiàng)計(jì)劃.（決心）