Unit2 Healthy Lifestyle
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Leading-in
While-class
After-class
Part.1 Leading-in
Leading in
阅读活动1所给的其他句子，讨论并归纳斜体部分（不定式）
在句子中的功能。
1 To change bad habits is never easy.
2 It took the surgeon three hours to finish my mother's lung 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 neighbours with loud music last
night.
Leading in
四个句子中的不定式都充当主语。用形式主语It代替
真正的主语 to change bad habits符合英语表达习惯，
避免句子头重脚轻、结构失衡。如果作者有意将比
较长的不定式主语放在句首，那么作者就是想要突
出不定式的内容。
Part.2 While-class
While-class
再次阅读 Reading and Thinking板块中的语篇，找出所有含
有不定式作主语的句子与同伴讨论答案。
However, during this period, it can be easy for some of them to form
bad habits.
To prevent harmful habits like these from dominating a teenager's
life is essential.
To change bad habits is never easy, even with many attempts.
After all, it is not easy to break bad habits.
While-class
动词不定式（短语）作主语
动词不定式（短语）作主语时，一般表示具体的、个别的、次性的或具有
将来意味的动作，作主语时，谓语动词通常用单数形式，具体用法如下：
1.用作主语的动词不定式（短语）常出现在谓语动词之后，这时需在句首
用形式主语It指代它。其句型有2种：
（1）It+v.+宾语/表语（+ for sb.）+ to do sth
当表语为名词或为描述动词不定式（短语）所表示的动作的特征的形容词
时，用for引出动词不定式（短语）的逻辑主语。这类形容词有 difficult，
easy，hard，important，interesting等。
While-class
例：
• It takes three generations to make a gentleman.[谚]十年树木，百年树人。（It+v.+名词短语+ to
do sth.）
• It is hard task to break up long habit in a short time.[谚]旧习难改。（It+be+名词短语+ to do sth.）
• It was easy to imagine the danger ahead of them.很容易想象他们前面的危险。（It+be+形容词+
to do sth.）
• It is against my principles to do such a thing.做这样的事违背我的原则。（It+be+介词短语+ to
do sth.）
• What a relief it is for us to succeed in our experiment at last！
我们的实验终于成功了，这对我们真是一个极大的安慰！
（it+be+名词短语+ for sb.+ to do sth.）
• It was hard for him to live on his small income.依靠他那点工资维持生活很难。（It+be+形容词+
for sb.+ to do sth.）
While-class
（2）It+v.+表语+of sb.+ to do sth.（表语常为表示人
的性格、品质的形容词，如good，kind，nice，
foolish，polite，ever，careless等。）
例：It was careless of you to leave your umbrella on
the train.
你真粗心，把伞忘在火车上。
While-class
2.动词不定式（短语）作主语可位于句首。
例：To do this is to cut the foot to fit the shoe.
这样做是削足适履。
While-class
3."疑问词+动词不定式（短语）"结构
动词不定式（短语）可与疑问词when、where、how、what、
which、who等组合，在句中作主语。
例：Where to hold the meeting is still unknown.会议地点还未知。
How to solve the problem has not been decided yet.如何解决这个
问题还未决定。
While-class
will take/ nutrition specialist/ a balanced diet menu/ make an
hour /for you
useful/ turn to fitness consultant/ for advice
illegal/ dangerous/ take / drugs
harmful/skip breakfast /often
It is useful to turn to a fitness consultant for advice.
It is dangerous to take drugs illegally.
It is harmful to often skip breakfast.
Part.3 After-class
While-class
1 A: Hello, doctor. I want to lose weight, but I just can't seem to do it.
What can you do to help me?
B: Well, first, it's necessary to what you eat. Cut
out all fatty food and sugary drinks, and eat more fruit and
vegetables
2 A: I really need to a way to exercise more. I could
use a fitness app, but my phone's full.
B: So delete a few files. I'm sure the app doesn't take up much space.
While-class
3 A: Before exercising, always do a few warm-ups
to .
B: I know. But then I always feel too tired to continue!
4 A: Should I go for the pizza or the fried chicken? I hate
like these. You know what—I'm going to eat both！
B: Wow! Don't eat too much junk food—you'll get fat. I've
actually to go on diet, so I'll just stick to the
fruit salad.
Summary
动词不定式（短语）作主语
动词不定式（短语）作主语时，一般表示具体的、个别的、次性的或具有将来意味的动作，
作主语时，谓语动词通常用单数形式，具体用法如下：
1.用作主语的动词不定式（短语）常出现在谓语动词之后，这时需在句首用形式主语It指代它。
其句型有2种：
（1）It+v.+宾语/表语（+ for sb.）+ to do sth
当表语为名词或为描述动词不定式（短语）所表示的动作的特征的形容词时，用for引出动词
不定式（短语）的逻辑主语。这类形容词有 difficult，easy，hard，important，interesting等。
（2）It+v.+表语+of sb.+ to do sth.（表语常为表示人的性格、品质的形容词，如good，kind，
nice，foolish，polite，ever，careless等。）
2.动词不定式（短语）作主语可位于句首。
3."疑问词+动词不定式（短语）"结构
动词不定式（短语）可与疑问词when、where、how、what、which、who等组合，在句中作主
语。
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