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2.You　　　 　to the meeting this afternoon if you have something important to do.　

　A. needn't to come　　 　　　　　　　　　　　　　　 B. don't need come 　C. don't need coming　　　　　　　　　　　　　　　　 D. needn't come

例1、There ____ be any difficulty about passing the road test since you have practised a lot in the driving school.

　 　　A. mustn’t 　　　　 B. shan’t 　　　　　　　　　　 C. shouldn’t 　　　　 D. needn’t

答案：C

[解析]　 根據經驗或慣例對某一情況進行推測，用should或ought to，常譯成“按理應該…”或“可能會……”。shouldn’t是其否定形式。

例2、-Is John coming by train?

-He should, but he _______ not. He likes driving his car.

A. must　　　 B. can　　　　 C. need　　　　 D. may

答案為D。

[解析]　 come, go, leave, start等趨向動詞的進行時表示將來時，所以答語是對這一將來動作做出的推斷。may not“可能不；不一定”，根據he likes driving his car可以看出John可能乘火車來，也可能自己開車來。may not正好符合這一語境。must not“不準”；cannot“不可能”；need not“不必”。　

例3、It is hard for me to imagine what I would be doing today if I _______ in love, at the age of seven, with the Melinda Cox Library in my hometown.

A. wouldn't have fallen　　　 B. had not fallen

C. should fall　　　　　　　　 D. were to fall

答案為B。

[解析]　 根據句意和I would be doing可以判斷這是虛擬語氣。at the age of seven 是表示過去的時間狀語，if從句中的謂語要用had not fallen，表示對過去情況的假設。由于主句中的謂語表示對現在的虛擬，條件句中的謂語表示對過去情況的虛擬，增加了試題的難題，但是，使用排除法可以容易地做出該題：should fall 和were to fall都可以用于條件句中表示對將來的虛擬；wouldn't have fallen不用于條件句中，所以都不能作為答案。譯文：如果我不在七歲時就迷戀上了我們家鄉的Melinda Cox圖書館，我真不能想象我今天會做什么。　

例4、You can't imagine that a well-behaved gentleman ________be so rude to a lady.

A. might　　　 B. need　　　　 C. should　　　 D. would

答案為C。

[解析]　 should用于表示感情，意向等句中的that從句，表示“竟然……，居然……”的驚訝，出乎意料。譯文：你難以想象一位行為體面的紳士會對一位女士那么粗魯。

例5、What would have happened ________, as far as up to the river bank?

A. Bob had walked farther　　　　 B. if Bob should walk farther

C. had Bob walked farther　　　　 D. if Bob walked farther

答案為C。

[解析]　 因為主句的謂語動詞用了would have happened，所以從句的謂語動詞要用過去完成時。在虛擬語氣中，如果條件狀語從句中的if省略，該句要倒裝。譯文：如果鮑勃走得遠一點，走到岸邊，會發生什么事呢?

例6、Mr. Bush is on time for everything. How ________it be that he was late for the opening ceremony?

A. can　　　　 B. should　　　 C. may　　　 D. must

答案為A。

[解析]　 can表示可能性的推測，常用于疑問句或否定句中；may表“可能性”常用于肯定句或否定句中；must常用于肯定句中表推測，“一定……”的意思。注意：can not表示“不可能”，而may not表示“或許不……可能不……”，兩者語氣上有區別。譯文：布什先生按時做好一切事。他來參加開幕式遲到了可能會是什么樣的情景呢?

例7、My sister met him at the Grand Theatre yesterday afternoon, so he _________ your lecture.

A. couldn't have attended　　　　　 B. needn't have attended

C. mustn't have attended　　　　　 D. shouldn't have attended

答案為A。

[解析]　 “情態動詞+不定式完成式”有各自的含義。must have done表示對過去事情的肯定推測，多用于肯定句中；needn't have done表示過去本不必做的事情；shouldn't have done表示過去做了不該做的事情；can't (couldn't) have done表示對過去的否定性推測，意為“不可能”。所提供的情境My sister met him at the Grand 表示他不可能參加講座。　

例8、He hesitated for a moment before kicking the ball, otherwise he_________ a goal.

A. had scored　　 B. scored　　　　 C. would score　　　 D. would have scored

答案為D。

[解析]　 根據otherwise可以判斷出要用虛擬語氣。表示過去發生的事要用would have scored。譯文：在踢球前他猶豫了一會兒，否則他就會射中球門。

例9、Oh, I'm not feeling well in the stomach. I _______ so much fried chicken just now.

A. shouldn't eat　 B. mustn't have eaten　　 C. shouldn't have eaten　 D. mustn't eaten

答案為C。

[解析]　 just now是表示過去的時間狀語。情態動詞在表示過去發生的事時，必須用“情態動詞+have+過去分詞的形式”。所以只能在選項B或C中確定答案。mustn't have eaten是一個錯誤選項，因為“mustn't+動詞”表示“禁止”，不表示判斷或推測。譯文：噢，我覺得胃不舒服。我剛才不應該吃那么多炸雞。　

例10、I was really anxious about you .You_________ home without a word.

A. mustn't leave　　　　　　　 B. shouldn't have left

C. couldn't have left　　　　　 D. needn't leave

答案為B。

[解析]　 should' t have done表示本來不應該做而做了，含責備意味。譯文：我真為你著急，你不應該不說一句話就離開了家。另外注意mustn't+動詞表示“禁止”。　

第三節 鞏固練習

Direction: Beneath each of the following sentences there are four choices marked A. B. C and D. Choose the best answer that completes the sentence.

1. -Isn' t that Ann's husband over there?

-No, it _______ be him . I'm sure he doesn't wear glasses.

A. can't　　　 　　 B. must not 　　　　　　 C. won't　　 　　　　　　　 D. may not

5、　 有suggest等詞的相應的名詞組成的同位語從句及表語從句用虛擬式。

例如：I accepted my mother’s suggestion that I should eat an apple every day .

4、　 有時句子通過but或otherwise等詞來表示真實與虛擬的轉換，在這種情況下，只有不真實的部分用虛擬式。

例如：I was ill yesterday；otherwise I would have played football with you .

But for the heavy rain , we would have gone to the concert .

3、　 某些條件可以用介詞短語without… , but for 等來表示 。

例如：Without your help , I could not have succeeded in passing the exam .

2、　 should與would都可以用于if條件句的主句中，但should一般只用于第一人稱，would用于所有人稱。

例如：If you were here , I would tell you the news .

1、　 在if條件句中，如果含有were , should或had等助動詞，if可以省去，句子用倒裝。

例如：Were I you , I would buy this reference book.

4、　 情態動詞后還可接不定式的進行式、完成式和被動式。

例如：He can’t be doing his homework now. 他現在不可能在做功課。

He must have attended the meeting last night. 昨晚他一定參加了會議。

(二)虛擬語氣

3、　 情態動詞的過去式，例如can-could，may-might。但是少數情態動詞只有過去式，例如used to表示過去常常。must的過去式往往用had to代替。

2、含有情態動詞的句子改為否定句或疑問句不必加助動詞，只需要將情態動詞置于主語前，或在情態動詞后加上not。

例如：Must I write a letter to cheer him up?

You needn’t wait for me.