whether to do or not和whether or not to do

whether to do or not和whether or not to do
请看下面一个选择题.
She can't decide whether____________.
A.to go or not B.or not to go C.or not to D.both A and B
答案是D
请问whether to do or not 和whether or not to do是一个意思吗?具体有什么用法?
不要牵扯到if,只谈whether!