it作形式主语与形式宾语

? It 代替不定式短语作形式宾语

1. He feels it his duty to help others. 他觉得帮助他人是他的责任。

2. The new medicine makes it possible to treat this terrible disease. 这种新药使治疗这种可怕疾病成为可能。

? It 代替动名词短语作形式宾语

1. We thought it no use doing that. 我们认为那样做无济于事。

2. Our teacher thinks it no good learning without practice. 我们的老师认为光学不实践是没有好处的。

? It 代替宾语从句作形式宾语

1. I think it very important that we take part in the discussion. 我认为我们参加这次讨论是很重要的.

2. Didn't I make it clear to you that I was not coming? 我不是向你明确表示过我不来了吗？

3. I hate it when people are talking with their mouth full of food. 我讨厌人边说话边嚼东西。（when引导的从句为定语从句，修饰it，而it又指代情形situation）

4. Tom takes it for granted that his parents should give whatever he wants. 汤姆总以为他的父母会给予他所有他想要的东西。

5. You must see to it that all the windows are closed before you leave the lab. 离开实验室前你务必要关上窗户。

6. The couple didn’t want it known that their house is empty. 这对夫妻不想让别人知道他们的房子没有人。

7. Why do you call it dinner when we are eating at noon? —We call it dinner when we have a lot to eat. 为什么你们把在中午吃的饭叫“正餐”？——我们凡是将吃的很多时的饭都叫“正餐”。