1、whether 和 if 都可用 it 作形式主语从句中。

2、如:
It's uncertain whether/if he'll come this evening.

1、不同之处1:whether可置于句首引导主语从句, if 则不能

2、如:
Whether the 2000 Olympic Games will be in Beijing is not known.

3、不同之处2:whether可引导表语从句 , if 则不能

4、如:
The question is whether it is not worth doing.
