It is a difficult job and they should be paid accordingly.

它是一項艱巨的工作，他們應該相應地獲得報酬

It is a physical impossibility to be in two places at once.

同時身處兩地在自然法則上是不可能的。

It is a very high quality production, brilliantly written and acted.

這是一部非常高質量的演出,絕妙地編寫而成並被表演出來。

It is a controversial policy which has attracted international censure.

這是一條有爭議的政策，已經遭到國際譴責。

it is important to learn english well.把英語學好很重要這裡的to learn english well就是主語 it 的內容，it 即為一個形式主語，這是動詞不定式做主語，it 也可以指一整句，比如，it is important that we should learn english well. 學好英語對我們來說很重要，這裡的we should learn english well就是形式主語 it 的內容。