must和have to
1.must表示有做某一動(dòng)作的必要或義務(wù)，強(qiáng)調(diào)主觀看法，可譯為“必須，應(yīng)該”。
Everyone must obey the rule.
人人都必須遵守制度。
We must do everything step by step.
我們必須逐步做每件事。
Teachers must be patient enough with their students.
老師必須對(duì)學(xué)生有足夠的耐心。
2.have to表示因客觀需要促使主語(yǔ)不得不做某事。
You can't turn right here. You have to turn left.
你不能在這里右拐，你必須左拐。
My eyesight is very poor. I have to wear glasses for reading.
我的視力很差，看書(shū)時(shí)不得不戴眼鏡。
You have to pass a test before you can get a driving licence.
你在取得駕照之前必須先通過(guò)考試。
提示：
在口語(yǔ)中，我們可以使用have got to來(lái)代替have to.
I've got to work on Sunday.
我不得不星期天工作。
When has Ann got to go
安必須什么時(shí)候走?
3.must與have to的比較。
must與have to在表示“必須”這個(gè)意思時(shí)意義相近，但在用法上有所區(qū)別。
①must含有說(shuō)話者的強(qiáng)烈決意(表示主觀的看法)，have to則表示外力環(huán)境或習(xí)慣使然(即表示客觀的必要，作“不得不”解)。
I must study hard.
我必須努力學(xué)習(xí)。(發(fā)自內(nèi)心的決定)
I have to study hard.
我不得不努力學(xué)習(xí)。(外界因素逼迫)
You must stay for supper.
你必須留下來(lái)吃晚飯。(because I want you to)
You have to stay for supper.
你得留下來(lái)吃晚飯。(because there is nowhere else to go)
②must只有一種形式，而have to可有多種時(shí)態(tài)。
They had to put off the sports meet due to the bad weather.
由于壞天氣，他們不得不推遲運(yùn)動(dòng)會(huì)。
These last two days he has had to take a rest at home.
這兩天他必須一直在家休息。
③must的否定式和have to的否定式的意思完全不同。
You must keep it a secret. You mustn't tell anyone.
你必須保密，你不可以告訴任何人。(mustn't表示“禁止”)
You don't have to tell me the secret.你不必告訴我這個(gè)秘密。
(don't have to意思是“沒(méi)有必要”= don't need to)
4.must用于表示推測(cè)，它的肯定程度比may, might, could大得多，一般只用于肯定句。
①must do (這里的do通常是狀態(tài)動(dòng)詞或系動(dòng)詞)，表示對(duì)現(xiàn)在狀態(tài)的推測(cè)。
He must be very lazy for his desk is very untidy.
他肯定很懶，因?yàn)樗恼n桌很不整潔。
Carol must get very bored with her job. She does the same thing every day.
卡羅爾肯定對(duì)她的工作厭煩了，她每天都做同樣的事。
②must be doing表示對(duì)現(xiàn)在動(dòng)作或狀態(tài)的推測(cè)。
Put on more clothes. You must be feeling cold with only a shirt on.
多穿點(diǎn)兒衣服，你只穿一件襯衣，肯定覺(jué)得冷。
③must have done表示對(duì)過(guò)去的動(dòng)作或狀態(tài)的推測(cè)。
The ground is wet. It must have rained last night.
地面是濕的，昨晚肯定下雨了。
I didn't hear the phone. I must have been asleep.
我沒(méi)聽(tīng)見(jiàn)電話鈴響，我一定是睡著了。
提示：
must表示推測(cè)只用于肯定句，否定句和疑問(wèn)句要用can, could來(lái)代替must。
He's just had his lunch. He can't be hungry already.
他剛吃過(guò)午飯，不會(huì)餓的。
They have just arrived here. They can't know many people.
他們剛到這里，不可能認(rèn)識(shí)很多人。
Leslie walked past me without speaking. He can'tcouldn't have seen me.
萊斯利從我身邊走過(guò)而沒(méi)打招呼，他肯定沒(méi)看見(jiàn)我。
5.must可用來(lái)表示根據(jù)邏輯推理必然要發(fā)生的事，可譯為“必然會(huì)，總是會(huì)”。
We all must die.
我們都會(huì)死。
Truth must be out.
真相必然會(huì)大白的。
Winter must be followed by spring.
冬天到了，春天還會(huì)遠(yuǎn)嗎?
6.must有時(shí)可用來(lái)表示“偏偏”的意思。
Why must it rain today
為什么偏偏在今天下雨?
When I was taking a nap, a student must knock at the door.
正當(dāng)我午睡時(shí)，偏偏一個(gè)學(xué)生在這個(gè)時(shí)候來(lái)敲門(mén)。
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