初中英語代詞情態(tài)動詞總結(jié)及練習(xí)題
you could (might) have been more careful. 你本來可以更細(xì)心的。
he needn’t have worried about it. 他本不必為此事?lián)摹?br>there was a lot of fun at yesterday's party. you ought to have come, but why didn't you?
昨天的聚會非常有意思。你本應(yīng)該來，為何不來呢？
2. 情態(tài)動詞后跟進(jìn)行式，表示“想必正在……”，“可能正在……”，“應(yīng)當(dāng)正在”等意。
it’s twelve o’clock. they must be having lunch. 現(xiàn)在是十二點(diǎn)。他們一定正在吃飯。
they may be discussing this problem. 他們可能正在論討這個問題。
he can’t be telling the truth. 他說的不可能是真話。
she shouldn’t be working like that. she’s still so weak. 她不應(yīng)當(dāng)那樣干，她身體仍那么虛。
（三）幾組詞的辨異
1. can 和be able to
1）情態(tài)動詞can只有兩種時態(tài)形式，現(xiàn)在式can和過去式could，而be able to有多種時態(tài)形式。
mary can play the piano. she has been able to play it since she was 5.
瑪麗會彈鋼琴。她五歲起就會彈了。
2）用在過去時中，could經(jīng)常表示能夠做某事，事實(shí)上不一定去做，而was∕were able to則表示“過去做成了某事”。在否定句中兩者可通用。
he couldm across the english channel. but he didn't feel like it that day.
他能游過英吉利海峽，但那天他不想游。
yesterday i was able to get home before the heavy rain. 昨天我在下大雨前趕到了家里。
2. must和 have to
must表示主觀意志，而have to表示由于客觀因素不得不做某事。must沒有過去式，除在間接引語中可用于表示過去時間，在直接引語中表示過去時間應(yīng)該用had to代替。
i told her that she must give up smoking. 我叫她必須戒煙。
we had to get everything ready that night. 我們那晚得把一切準(zhǔn)備就緒。
3. would和used to
1）used to表示過去與現(xiàn)在或過去某時與后來的情況有不同，而would只表過去的情況。
people used to think that the earth was flat.
過去人們認(rèn)為地球是平的。（現(xiàn)在人們不這么認(rèn)為。）
she would go out for a walk in the morning when she was in the country.
在鄉(xiāng)下時，她總是在早晨去散會兒步。（可能現(xiàn)在仍有散步的習(xí)慣。）
2）used to可表示過去的習(xí)慣動作和經(jīng)常的情況，而would只表示過去的習(xí)慣動作。
he used to ∕would smoke while writing. 過去他寫東西時常抽煙。
she used to be fat. 她過去很胖。