if不能与or或者or not连用.
例如：下面两句中的whether 都可以用if 代替
I wonder whether she will be able to come.
我怀疑她是否能来.
I don't know whether it's large enough.
我不知道这是否够大.
但下面各句中只能用whether
You haven't answered the question of whether you'll go with us or not.
你还没有回答你是否跟我们去的问题.
I don't know whether to go or stay.
我不知道是去还是留.