I think it bad manners to smoke in a reading room.为什么不用it's,是不是老师说错了？

Question

相同的I think it impolite to smoke in a reading room,这是什么语法？

Answer 1

1. 用it或用it's都是可以的。

2. 如果用it's，则使用一个省略that的宾语从句，且宾语从句的结构是一个固定句型：it is + 形容词/名词 + to do sth.
即：I think it's bad manners to smoke in a reading room.
= I think (that) it is bad manners to smoke in a reading room.
I think it's impolite to smoke in a reading room.
= I think (that) it is impolite to smoke in a reading room.

3. 如果单独使用it，则采用了以下固定结构：
及物动词think + 形式宾语it + 宾语补足语（名词/形容词）+ 真正宾语（不定式）。
因为做宾语的不定式太长，放在中间会显得此句头重脚轻，所以一般将其后置，并使用it去做形式宾语。
类似的动词有五个：think, feel, make, find和consider.
再如：I find it difficult to learn English well.
= I find (that) it is difficult to learn English well.

参考资料：英语牛人团

Answer 2

这里it作形宾

think/ find/ feel/ consider/ make/ regard/take it for granted /see to

1.I find it pleasant to work with him.
(it 作形式宾语，代替不定式短语to work with him)
我觉得和他一起工作很愉快。
2.They felt it difficult to finish the work in such a short time.
（ it 作形式宾语，代替不定式短语to finish the work in such a short time）
他们认为在这么短的时间内完成这项工作是困难的。

3.She thinks it her duty to help us.
（ it 作形式宾语，代替不定式短语to help us）
她觉得帮助我们是她的责任。

4.I think it my honor to be invited to speak here.
（ it 作形式宾语，代替不定式短语to be invited to speak here）
我觉得应邀在这儿演讲是我的荣耀。

5.Tom didn’t find it difficult to write letters in Chinese.
（ it 作形式宾语，代替不定式短语to write letters in Chinese）
汤姆发现用汉语写信不难。

6.All these noises made it impossible for me to go on with the work.
（ it 作形式宾语，代替不定式短语to go on with the work）
这些噪音使我无法继续工作。本回答被提问者采纳

Answer 3

it在这里作形式宾语