2016屆高考英語語法知識情態動詞和虛擬語氣復習
might(may)+ have done：對過去發生的行為不太肯定的推測。he may not have finished the work.if we had taken the other road, we might have arrived earlier.must+ have done：對過去發生的行為肯定的推測。其否定式為：cannot have done。you must have seen the film.you cannot have seen the film.needn’t+ have done：本來不必要做的而實際上又做了。you needn’t have watered the flowers,for it is going to rain.注意：didn’t need to(have to)do：沒有必要做而實際上也沒有做i didn’t need to clean the windows.my sister did it 2 hours ago.should(ought to)+ have done：本來應該做而實際上又沒有做。其否定形式表示某中行為不該發生卻發生了。you should have started earlier, but you didn’t.she shouldn’t have taken away my measuring tape,for i worked to use it.注意：he should have finished the work by now.（表推測）虛擬語氣
類 別
用 法
例 句
if引導的
條件從句與現在事實相反從句動詞：過去式（be用were）主句動詞：should/would/could/might+doif he were here, he would help us.與過去事實相反從句動詞：had+done主句動詞：should/would/could/might+have+doneif 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+to do主句動詞：should/would/could/might+動詞原形if it should rain tomorrow, we would not go camping.
省略if的虛擬條件句將虛擬條件從句中的were，had,should放到主語之前，構成主謂倒裝①should he come ,tell him to ring me up.②were i you,i would not do it.③had i been free,i would have visited you.
混合虛擬條件句
不同時間的虛擬：各遵守各的規則①if he had listened to me, he would not be in trouble now.②if he had told me yesterday,i should know what to do now.③if i were you, i would have gone to her birthday party.
虛擬與陳述的混合：各遵守各的規則①he could have passed the exam,but he wasn’t careful enough. ②you should have come earlier.the bus left a moment ago.
含蓄虛擬
條件句
but for+名詞表示虛擬條件句子或主句中的謂語動詞的形式視具體情況而定。這是考查考生應變能力的最佳試題。---but for your timely warning,we ______ into great trouble.---you know we’re friends.a. would get b. must have got c. would have got d. can’t have got
without+名詞表示虛擬條件without the air to hold some of the sun's heat, the earth at night would be freezing cold.
動詞不定式表示虛擬條件it would be only partly right to follow in this way.
如果用這種方式，僅僅對了一半。
現在分詞表示虛擬條件having known in time ,we might have prevented the accident.要是及時得知的話，我們也許能阻止這場事故。