文档介绍：Unit 3:
Under the sea
语态
时态
主动形式
被动形式
一般式
完成式
(not) doing
(not) being done
(not)
having done
(not)
having been done
动名词 的用法：
Swimming is good for health.
Raising your hat to a lady is good manners .
对一位女士脱帽致敬是礼貌的。
Being killed by sharks in the sea is a common thing .
动名词作主语时，还可以用it作形式主语：
It is no good waiting here.
It is no use crying over spilt milk.
覆水难收。
It is a waste of time talking to him .
注意
动名词和不定式都可以作主语，动名词作主语表示一般或抽象的多次性行为，不定式作主语往往表示具体的或一次性的动作。如：
Playing with fire is dangerous.
（泛指玩火）
To play with fire will be dangerous.
（指一具体动作）
2. 作表语
Teaching is learning. 教学相长.
My hobby is making model planes.
What worried the child most was
not being allowed to visit his mother
in the hospital .
动名词和不定式都要有对称性;当主语是不定式时，表语也用不定式；反之，当主语是动名词时，表语也用动名词。
To see is to believe.
= Seeing is believing.
注意
动名词既可作动词的宾语, 也可作介词的宾语。
We would appreciate hearing from
you. 我们会珍惜你的来信。
The bird escaped being caught.
I feel like joining the army.
He was afraid of being abandoned by us.
注意： 在 admit, advise, avoid, appreciate, allow, consider, delay, enjoy, envy, escape, excuse, finish, forgive, forbid, imagine, mind, miss, practise, permit, risk, suggest, give up, put off, feel like, understand, insist on , look forward to, object to, keep（on）等后只接动名词作宾语。
注意
1. 在want，need，require，deserve等动词之后作宾语时，常用动名词的主动式表示被动意义。
Your car needs filling. 你这车要充气了。 This city deserves visiting. 这座城市值得光顾一下。 The problem requires studying
carefully . 这个问题需要认真研究。 The trees want watering . 这些树需要浇
水了。