易混易错点1：He paused for a moment wondering whether to turn back as the captain urged him.
whether和if的用法区别 1)whether和if常用来引导宾语从句，这时两者的含义区别很小，一般可通用。
I don't know whether/if they will come to help us. 我不知道他们是否来帮助我们。
I am not sure whether/if I'll have time to go with you.
我很难说我们是否有时间跟你们一起去。 上面两句无区别。
但是，当whether与or not连成一个词组时，whether不可换用if。
I don't know whether or not they will come for our help.
我不知道他们是否要来求我们支援。
