讲义
如句子的主词含有不定词词组 (for + NP) + to V，常用it代替，再把不定词词组移到后面。

To work with you is nice. = It is nice to work with you.

跟你在一起工作真好。

To study English every day is important. 每天读英文很重要。

= It is important to study English every day.

To learn two foreign languages at the same time is difficult.

= It is difficult to learn two foreign languages at the same time.

同时学两种外国语言蛮困难的。

To make a reservation in advance is necessary.事先订位是有必要的。

= It is necessary to make a reservation in advance.

To get him to change his mind is not easy. 要让他改变心意不容易。

= It is not easy to get him to change his mind.

To tip waiters is customary in America.

在美国给服务生小费是一种习惯。

It is customary to tip waiters in America.