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本課複習：情態動詞的用法
新二Lesson 17
情態助動詞must的用法
一般譯為“必須”，可以表示“必要”、“命令或強制”。沒有時態和人稱變化。通常只用於現在時和將來時。在其他時態中，must有時和have to或have got to可以互換。用於第一人稱時，have to和have got to強調客觀的要求或外在的原因，must則強調主觀的要求或表示說話的人認為自己有權做某事
must還表示肯定的推測
She must be at least thirty-five years old.
表示肯定的推測
Jennifer will have to take part in a new play soon.
客觀原因，將要參加一個新演出
In the play, she must appear in a bright red dress and long black stockings. Last year in another play, she had to wear short socks and a bright, orange-coloured dress.
must和have to的互換
新二Lesson 41
在表達“必要”、“不必要”等含義時，除了可用must和 have（got）to以外，還可以用need。need只有情態助動詞的部分特徵，僅用於某些疑問句和否定句。need用於疑問句時，問者往往希望得到 否定的回答
‘You needn't be so rude about it,' my wife answered as she looked at herself in the mirror.
as引導時間狀語從句本句。本句的need是個情態動詞，只能用於否定和疑問句。肯定句用must,have to,ought to或should
‘We mustn't buy things we don't need,'I remarked suddenly.I regretted saying it almost at once.
mustn't表示絕對禁止。在說話人看來，根本沒有選擇餘地。這麼說話未免太粗暴，所以後邊的句子說馬上後悔這麼說話。
‘You needn't have said that,' my wife answered.
needn't have done表示本來不該做某事，但是已經做了 常用的類似詞would should動能這麼用
新二Lesson 65
He should have known that the police would never allow this sort of thing.
新概念三Lesson 11
You should have declared that
你本該申報的。實際沒有。都是一種虛擬
新概念三Lesson 58
At least sorting out the things she should have discarded years ago was now being made easier for her.
在很多年前她本該扔掉的那些東西
新二Lesson 65
表示“應該”和“必須”的情態助動詞 should, ought, have to 與must
should和ought to都可譯為“應該”，表示義務、責任或某個正確的行為。
ought to比should語氣略強些，多用於肯定句
疑問句與否定結構則多用should。
與它們相比，must和 have to 的語氣要強得多，沒有選擇餘地
A policeman approached Jimmy and told him he ought to have gone along a side street as Jumbo was holding up the traffic.
本應該實際上沒有。as原因狀語從句
so it was fortunate that we didn't have to carry him.
have to的否定形式，不必
本課
標題A slip of the tongue，舌頭的一滑，口誤
When the news got round that a comedy show would be presented at our local cinema by the P. and U. Bird Seed Company, we all rushed to see it.
嚯，好長的句子！when引導的時間狀語從句。在從句中，that引導的同位語從句
We had to queue for hours to get in and there must have been several hundred people present just before the show began.
had to過去時，不得不。must have been表示對過去肯定的推測。在演出開始前，場內肯定已經有好幾百人了
Those who failed to get in need not have felt disappointed, as many of the artistes who should have appeared did not come.
need not have felt沒有必要感到失望
should have appeared did not come.那些本該出現的藝術家都沒來
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