高中英語(yǔ)詞法專題情態(tài)動(dòng)詞精品教案
6. must 與have to
1). 一般情況下，兩者可互換。 must = have to
2). must “必須，應(yīng)該”表示說(shuō)話人的主觀看法，即說(shuō)話人認(rèn)為必須干某事。
（內(nèi)在原因）
have to “必須，不得不”強(qiáng)調(diào)客觀需要，即外界因素迫使某人不得不干某事。（外界原因）
i can’t stop playing the computer games. for your health, i’m afraid you ______.
a. can b. may c. must d. had to
二.情態(tài)動(dòng)詞后跟完成式和進(jìn)行式的用法
1. 情態(tài)動(dòng)詞后跟完成式，表“原本應(yīng)該干某事，而實(shí)際上沒(méi)干”
i should have finished the work earlier.
he isn’t here. he must have missed the train.
2. 情態(tài)動(dòng)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.
they may be discussing this problem.
he can’t be telling the truth.
she shouldn’t be working like that. she’s still so weak.
三.情態(tài)動(dòng)詞的同義轉(zhuǎn)換.
1. can = be able to
2. must = have to
3. needn’t = don’t have to
4. need do sth = need to do sth .