A be,have和do(主要的助动词)
1 在否定句和疑问句中,be与do的用法遵从助动词的下列规则:
否定句中,助动词+not:
He isnt coming.
他不来了。It did not matter.
没关系。
疑问句中,主语+助动词:
Was he waiting?
他当时在等吗?
Does she see us?
她看到我们了吗?
2 have 在疑问句及否定句中的位置一般与助动词相同:
Has he(got)to go?
他一定得走吗?
但有时也用do/did形式:
Does she have to go?
他一定得走吗?
3 be与带to的动词不定式连用:
They are to wait for us at the station.
他们将在车站等我们。
have后也可接带to的动词不定式,但有两种结构除外。
do与不带to的不定式(即动词原形)连用:
Did he write?
他写信了吗?
4 be(参见第115节),have和do作助动词使用时,需要带分词或不定式,但在答句或评语等中常省略。
Have you seen it?
Yes,I have(seen it).
你看见了吗?
是的(,我看见了)。
5 在be,have和do作普通动词使用而有自己本身的意思,如have有拥有的意思、do有干/从事的意思等(参见第126节)时,它们只能是句子中唯一的动词:
He is lazy.
他很懒惰.
He has no job.
他没有工作。
He does nothing.
他什么事也不干。
在这种情况下,do与助动词do/did连用:
What do you do in the evening?
你一般晚上做什么?
have可以用两种方法进行变化,即用助动词do/did或不用:
Have you(got)time?/Do you have time?
你有空吗?
B can,could,may,might,must,ought,will,would,shall和should 是情态动词,也称情态助动词。
情态动词的第三人称单数后不加s:
I must我必须
he must他必须
I can我可以
he can他可以
它们在构成否定形式和疑问形式时均遵循助动词的规则:
will not ought not
will he? ought he?
它们没有真正的过去时态。情态动词有四种过去形式,即could,might,should和would,但用途有限。
情态动词没有不定式或分词形式,所以不能用于进行时态。
除ought之外其他情态动词后一律跟不带to的动词不定式(即动词原形):
You should pay.
You ought to pay.
你应该付钱。
情态动词后面应带动词原形(而非分词等),但有时可省略:
Can you understand?
Yes,I can(understand).
你明白吗?
是的(,我明白)。
C need,dare和used(半情态动词)
1 当need和dare作助动词时,可遵循情态动词的句式,后面跟不带to的动词不定式:
He need not wait.
他不用等。
但也可与do/did形式连用,这时后面要接带to的动词不定式:
He doesnt dare to interrupt.
他不敢插嘴。
They didnt need to wait.
他们不需要等。
need和dare也可作普通动词用,有词形变化,并可与分词连用:
He needs help.
他需要帮助。
They dared me to jump.
他们激将我,要我跳下去。
2 used有时说成used to,只指过去的事。它的否定式和疑问式常常遵循助动词的规则:
I used not/usednt to go.
我一向不去。
虽然严格来讲used不带不定式,但经常可以听到didnt use to 和did he/she等+use to?的形式。
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