539　It is +形容词／名词+for sb.+to do sth.

　动词不定式用作主语时，常用it 作形式主语，放在句首，而把真正主语不定式移到句尾，这就是It is +形容词／名词+(for sb.) +to do sth. 结构的来源。如果点明不定式动作的执行者，即不定式的逻辑主语，就在不定式前加上for sb., 表示“对……来说”。参见本书有关部分。

It is easy for me to read the book. 对我来说，读这本书很容易。

It is important for us to learn English well. 对我们来说，学好英语是重要的。

Is it necessary for us to leave so early? 我们这么早动身有必要吗？

It is really hard for Jim to pass the entrance examination. 对吉姆来说通过入学考试真的很难。

It is possible for Tom to finish the work before Friday. 汤姆有可能在星期五前完成这项工作。

It is a good idea for us to travel to the north. 去北方旅行对我们来说是个好主意。

It is easy to climb up the ladder. 爬上那个梯子很容易 。

It is not hard to climb up the ladder.

to climb up the ladder is easy.

It is hard to do the job. 这项工作很难做 。

It is not easy to do the job.

to do the job is hard.