備戰2019屆高考英語（通用版）一輪復習專題12 情態動詞
he ought not to have thrown the old clothes away.（事實上已扔了。）
ought to 在語氣上比should 要強。
4)needn’t have done sth.本沒必要做某事
i dressed very warmly for the trip，but i needn’t have done so.the weather was hot. 那次旅行，我穿的非常暖和，但我本沒有必要那么去做。天太熱了。
5)would like to have done sth.
本打算做某事
i would like to have read the article，but i was very busy then.
我本想讀那本書，但我那時太忙了。
7.should 和ought to
should 和ought to 都為“應該”的意思，可用于各種人稱。
—ought he to go?
—yes.i think he ought to.
表示要求，命令時，語氣由 should（應該），had better最好），must（必須）漸強。
8.had better表示“最好”
had better 相當于一個助動詞，它只有一種形式，它后面要跟動詞原形。
had better do sth.最好干某事
had better not do sth.最好不干某事
had better have done sth.表示與事實相反的結果，意為“本來最好”。
9.would rather表示“寧愿”
would rather do 寧可干某事
would rather not do 寧可不干某事
would rather...than... 寧愿……而不愿
還有would sooner，had rather，had sooner都表示“寧愿”“寧可”的意思。
i would rather stay here than go home.=i would stay here rather than go home.
我寧可待在這兒也不回家。
10.will和would
1)would like；would like to do=want to 想要，為固定搭配。
would you like to go with me?你想和我一塊兒去嗎？
2)will you...? would you like...?表示肯定含義的請求勸說時，疑問句
中一般用some，而不是any。
would you like some cake?要蛋糕嗎？
3)否定結構中用will，一般不用would，won’t you是一種委婉語氣。
won’t you sit down?你不坐嗎？
11.情態動詞的回答方式
問句 肯定回答 否定回答
need you...? yes，i must.
no,i needn’t
must you...?/ don’t have to.
12.帶to 的情態動詞
帶to 的情態動詞有四個：ought to，have to，used to，be to，如加上have got to(=must)，be able to，為六個。它們的疑問，否定形式應予以注意：
do they have to pay their bill before the end of the month?
she didn’t use to play tennis before she was fourteen.
you ought not to have told her all about it.
ought he to see a heart specialist at once.
ought to 本身作為情態動詞使用。其他的詞作為實義動詞使用，變疑問、否定時，須有do 等助動詞協助。
13.比較need和dare
這兩詞既可作實義動詞用，又可作情態動詞用。作為情態動詞，兩者都只能用于疑問句，否定句和條件句。 need 作實義動詞時后面的不定式必須帶to，而dare作實義動詞用時，后面的to 時常可以被省略。
1)實義動詞：need（需要，要求） need+n./to do sth.
2)情態動詞：need，只用原形need后加do，否定形式為need not。