from，to是什么词性

from to是介词词性

例句

1、

She has to work at weekends from time to time.

她偶尔周末还得工作。

2、

The number of new students decreased from 210 to 160 this year.

今年新生人数从210减少到160。

3、

The transition from school to work can be difficult.  

从在学校念书到上班工作，这一转变有时候可真不容易。