高考英语总复习 语法专题 第九讲 情态动词和虚拟语气精练精析 新人教版

第九讲情态动词和虚拟语气

一、情态动词考点透析

1．can (could)，be able to。

can只有现在式can和过去式could两种形式， be able to可用于现在式、过去式、将来时、完成时。要表示“能够做某事”，可用can或be able to，但若要说过去的确运用了某种能力做成了某件事情，就只能用was/were able to，表将来具备的能力只能用will/shall be able to。

(1)If you study hard，you will be able to express freely in English in three months.

(2)The fire spread through the hotel very quickly but everyone was able to get out.

2．could是can的过去式，但是在很多情况下，特别是在口语中，它表示语气的委婉。因此，用could提问时，不能用could回答，而要用can或may。would，might用于疑问句时也表委婉语气，回答时应该用will，may。

(1)－Could I borrow your dictionary?

－Yes，of course you can.

(2)－Could I call you by the first name?

－Yes，you may.

(3)－Would you be so kind as to explain the word?

－Yes，I will.What is it?

3．may/might，can/could都可表示可能，但may/might 不能用于问句，can/could用于否定句、疑问句、感叹句，表示惊异、怀疑，一般不用于肯定句。如果用于肯定句，则表示偶尔发生某事的可能，或某人某物一时的特点。

(1)－Are you coming to Jeff's party?

－I'm not sure.I might go to the concert instead.

(2)－Where can Mr.Li be?

－Sorry，I don't know.You can go to ask Mr.Zhang.He may help you.

(3)Mr.Bush is on time for everything.How can it be that he was late for the opening ceremony?

(4)We enjoy good weather in January，but sometimes it can be terribly cold.

4．must表推测用于肯定句，其否定式要用can't。

对现在表示推测：

must do；can't do

对正在进行的动作表示推测：

must be doing；can't be doing

对过去表示推测：

must have done；can't/couldn't have done

(1)－There were already five people in the car，but they managed to take me as well.

－It couldn't have been a comfortable journey.

(2)Jack can't have arrived yet，otherwise he would have telephoned me.

(3)Put on more clothes，you must be feeling cold with only a shirt on.

(4)I didn't hear the phone.I must have been asleep.

5．情态动词完成式的意义。

can/could have done

过去可能做过，过去本来可以做某事但没有做

must have done过去一定做过

may have done可能已经做过，本来可以做但没做

might have done过去可能做过，过去本来可以做但没做

can't/couldn't have done过去不可能做过某事

should (not)have done

过去本该(不该)做，但却没做(做了)

ought (not)to have done

过去本该(不该)做，但却没做(做了)

needn't have done过去本来没必要做，但却做了

would rather (not)have done宁愿过去做了(没做)

注意：must have done，may have done，might have done，can't have done都表推测。其区别在于可能性的大小。must have done表很有可能，may have done表有可能，might have done表可能性很小，can't have done则为“不可能”。

(1)I told Sally how to get here，but perhaps I should have written it out for her.

(2)Sorry，I'm late.I might have turned off the alarm clock and gone back to sleep again.

(3)I was really anxious about you.You shouldn't have left home without a word.

(4)Tom needn't have got up that early since it was Sunday and he had nothing important to do.

(5)I would rath er not have blamed him because he was a child after all.

6．关于should的主要用法。

(1)It's already seven o'clock.Jack should be here at any moment.

(should表推测，意为“随时都会来”，“真该来了”。)

(2)－When can I come for the photos? I need them tomorrow afternoon.

－They should be ready by 12：00.(should：应该)

(3)You can't imagine that a well­behaved gentleman should be so rude to a lady.

(should表惊异，意为“居然”、“竟然”)

(4)If he should fail to come，ask Mr.Zhang to attend the cer emony instead.

(should表语气较强的假设，意为“万一”)

(5)We should have studied last night，but we went to the concert instead.(should have studied：我们本该学习的，但却没有学习)

7．关于shall的用法。

shall用于第一人称、第三人称疑问句中，表示说话人征求对方意见或向对方请示。

shall用于第二、第三人称，表示说话人给对方的命令、警告、允诺或威胁。

(1)Shall I go on reading the text?

我要继续读课文吗？(shall：征求意见)

(2)You shall be punished one day for what you've done.

总有一天你会因你的所作所为受到惩罚的。

(shall：威胁，警告)

(3)He shall get what he deserves.I promise it.

他会得到他应该得到的，我保证。(shall：允诺)

强化训练一

按照句子结构的语法性和句子连贯的要求，在空白处填上适当的情态动词或根据提示使用正确形式的情态动词

1．I ________ (not) use a clock to wake me up because at six o'clock each morning the train comes by my house.

2．I________ (not) thank you too much for all your help to my son while we were away from home.

3．—________ you interrupt now? Can't you see I'm on the phone?

—Sorry Sir, but it's urgent.

4．I got close enough to hear them speaking Chinese, and I said “Ni Hao” just as I ______do in China.