（2）whether和if的用法。
①whether和if在宾语从句中可以互换，但是作介词宾语时连接词一般用whether.如：
It all depends on whether they will come back.
②后面直接跟or not 时用whether.如：
I didn’t know whether or not he had arrived in Wuhan.
③主语从句表语从句中只能用whether.如：
Whether the meeting will be put off has not been decided yet.
The question is whether they have so much money.
④whether可以引导同位语从句，用以说明前面的名词的内容，if不能。如：
We ought to discuss carefully the question whether we can do it or not.
⑤whether常与or连用表示一种选择，if不能这样用；whether也可与动词不定式连用但if不能。如：The question of whether they are male or female is not important.
I have not decided whether to go or not.
⑥间接引语位于句首时或者是间接引语提前时用whether不用if.如：
Thank you， but whether I’ll be free I’m not sure at the moment.
⑦whether可引导一个让步状语从句表示“不管”、“无论”，而if不能。如：
Whether he comes or not， we will begin our party on time.
（3）疑问词 ever和no matter 疑问词的区别。
①疑问词 ever可引导名词性从句，在主从句中要充当一定的部分。如：
Whoever breaks the rule must be punished.
You can choose whatever you like in the shop.
②疑问词 ever还可引导让步状语从句。如：
Whoever breaks the rule， he must be punished，
Whatever you do， you must do it well.
③no matter 疑问词只能引导让步状语从句。如：
No matter what you do， you must do it well.