It 代替动名词短语时：
We thought it no use doing that.
我们认为那样做无济于事。
Our teacher thinks it no good learning without practice.
我们的老师认识光学不实践是没有好处的。
It 代替宾语从句时：
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
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？