2022屆高考英語情態(tài)動詞和虛擬語氣
⑦should(ought to)+ have done：本來應(yīng)該做而實際上又沒有做。
其否定形式表示某種行為不該發(fā)生卻發(fā)生了。
you should have started earlier, but you didn’t.
she shouldn’t have taken away my measuring tape, for i wanted to use it.
注意：本結(jié)構(gòu)還可以表“推測”的意思
he should have finished the work by now.
到現(xiàn)在他應(yīng)該已經(jīng)做完那項工作了。
11.其它情態(tài)動詞
①have to
have to表示 “必須, 不得不”, 在這個意義上與must很接近, 但must表示的是說話人的主觀看法, 而have to表示的卻是客觀需要. have to比must有更多的形式。
the tv set is broken. i have to buy a new one.
the students will have to know how to use the computers.
注意：在回答must的問句時, 否定式常用need not(needn’t)或don’t have to表示 “不必”。而不用
must not, 因為must not表示 “不可以”。
②used to
表示過去的習慣動作或狀態(tài)(現(xiàn)在已不復(fù)如此)
—did you use to go there to see your brother? /used you to go there to see your brother?
—yes, i did(used to). /no , i didn’t (usedn’t).
注意：would也可表示過去反復(fù)發(fā)生的動作或某種傾向，但是不涉及到現(xiàn)在。
③had better
表示 “最好(做……)”
we had better go now.
其否定式為had better not
ii.虛擬語氣
(一)一般虛擬結(jié)構(gòu)
類別 用法 例句
if引導(dǎo)的條件從句 與現(xiàn)在事實相反 從句動詞：過去式（be用were）
主句動詞：should/would/could/might+動詞原形 if he were here, he would help us.
與過去事實相反 從句動詞：had+過去分詞
主句動詞：should/would/could/might+have+過去分詞 if i had been free, i would have visited you.
與將來事實相反 從句動詞：過去式 / should+動詞原形 / were+不定式
主句動詞：should/would/could/might+動詞原形 if it should rain tomorrow, we would not go camping.
注意:主句中的should只用于i、we，但在美國英語中，should常被would代替;從句中的should可用于各種人稱，且不可以被would所代替。
(二)混合虛擬結(jié)構(gòu)
1.不同時間的虛擬
if he had listened to me, he would not be in trouble now.(從句與過去事實相反，主句與現(xiàn)在事實相反)
if he had told me yesterday, i should know what to do now. (從句與過去事實相反，主句與現(xiàn)在事實相反)
if i were you, i would have gone to her birthday party. (從句與現(xiàn)在事實相反，主句與過去事實相反)
if you hadn’t lent me some money, i couldn’t have bought the new house and most likely i would be still living in the dangerous house now. (從句與過去事實相反，and后面的主句與現(xiàn)在事實相反)
2.虛擬與陳述的混合
he could have passed the exam, but he wasn’t careful enough.
you should have come earlier. the bus left a moment ago.
(三)特殊句式虛擬結(jié)構(gòu)