欢迎访问贝贝英语网！
Look at the following sentences and pay attention to the italicized infinitives. Find more infinitives in the reading passage, and tell their meanings and functions.
1. To change bad habits is never easy.
2. It took the surgeon three hours to finish my mother’s ling surgery.
3.To join the people’s Liberation Army, it is required for men to shave off their beards.
4. It was not polite to disturb your neighbors with loud music last night.
1….it can be easy for some of them to form bad habits.
2. After all, it is not easy to break bad habits.
动词不定式在句中做主语，有时为了保持句子的平衡，避免头重脚轻，常用it做形式主语，而真正地主语放在句子的末尾。比如第2；3；4例句。
动词-ing形式和不定式作主语, 都是说明一个内容。
不定式通常表示一个将来的、具体的内容;
但是, 而动词-ing形式则表示一种经常性的、习惯的或抽象的概念。
To look after children is her job today.
她今天的工作是看孩子。
Looking after children is her work.
她的工作是照顾孩子。
不定式作主语，it 做形式主语的常见结构：
It is +adj.+(for sb) to do
It is easy for me to learn how to drive.
学开车对我来说很轻松。
It is +adj.+(of sb) to do
It is clever of you to apply for the position.
你申请这个职位真是明智的。
It is +n.+ to do sth( an honour, our duty, a pity, a shame)
It is our duty to take care of you.
照顾你是我们的责任。
It takes/took sb some time to do sth.
It takes me half an hour to do my housework.
我花了半个小时做家务。
