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關(guān)閉窗口 有時后接動詞完成進(jìn)行式, 表示“一定(一直)在……”：
Someone must have been using it. The cover is off. 準(zhǔn)是一直有人在用它, 蓋子都取下來了。
9. must與have to用法區(qū)別
I haven’t got enough money to buy a ticket, so I ______ go home on foot.
A. must B. have to C. ought to D. may
此題應(yīng)選B。從句意上看, 只能選A, B。關(guān)于must 和haveto 表示“必須”時的區(qū)別, 注意以下幾點(diǎn)：
1. 強(qiáng)調(diào)重點(diǎn)不同：must強(qiáng)調(diào)主觀;而have to強(qiáng)調(diào)客觀：
You must go now. (I want you to go now). 你必須現(xiàn)在就走(有“我要你現(xiàn)在走”之意)。
If I buy that car, I’ll have to borrow some money. 如果我要買那輛汽車, 我得借些錢。
2. 時態(tài)形式不同：一般說來, must 只有現(xiàn)在時一種形式(在賓語從句中可表示過去), 而have to則有多種時態(tài)形式：
He said (that) she must go with me. 他說她一定要同我一起去。
She had to go there on foot yesterday. 昨天她不得不步行去那兒。
He has had to buy a car. 他不得不買了輛小汽車(www.hz123456.com)。
3. have to可以有分詞、動名詞、不定式等非謂語形式, 而must則沒有這些形式：
He only saw her in the evening, having to be awayall day. 他因整天得外出, 所以只能晚上見她。
I regret to have to trouble you again. 我很抱歉不得不再麻煩你一次。
4. 否定式的意義不同：must 的否定式mustn’t意為“不準(zhǔn)”、“不允許”；而 have to的否定式 don’t have to意為“不必”(=needn’t)。
10. 你知道need的這些用法嗎
I got up early, but I ______ so, because I had no work to do that morning.
A. needn’t do B. needn’t have done C. didn’t need do D. didn’t need to do
此題應(yīng)選B。為了弄清此題, 首先我們要知道need有情態(tài)動詞和實(shí)義動詞兩種用法。一般說來, 這兩種用法在意思上沒有什么差別, 只是用法差別較大：
他必須去那兒嗎?
正：Need he go there? (need為情態(tài)動詞)
正：Does he need to go there? (need為實(shí)義動詞)
但有時候兩種用法在意思上也有較大差別：
1. a. He needn’t be told. 沒有必要告訴他。
b. He doesn’t need to be told. 不需要告訴他了。 (即：他已知道了)
2. didn’t need to do / needn’t have done：前者表示因?yàn)闆]有做某事的必要, 所以沒有去做;后者表示某事已經(jīng)做了, 但后來覺得沒有必要去做, 含有責(zé)備或遺憾之味：
I didn’t need to get up early this morning, so Istayed in bed until
That computer was expensive, and what’s more, I didn’t need to buy such a good one. 那臺電腦很貴, 況且我也沒有必要買那樣好一臺電腦。
I was the first to get there. I needn’t have gonethere so early. 我是第一個到那兒的人, 我本來不必去那么早的。
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