whether 和whether or not的问题

请问：whether/ whether or not有什么区别吗？为什么ets说用whether就不必用whether or not?如og-87黄色部分

87. Beyond the immediate cash flow crisis that the museum faces, its survival depends on if it can broaden its membership and leave its cramped quarters for a site where it can store and exhibit its more than 12,000 artifacts.

(A)  if it can broaden its membership and leave

(B)   whether it can broaden its membership and leave

(C)  whether or not it has the capability to broaden its membership and can leave

(D)  its ability for broadening its membership and leaving

(E)   the ability for it to broaden its membership and leave

Choice A is faulty because it uses the unidiomatic construction depends on if; whether is required to connect depends on with the clause beginning it can....

Choice C uses whether or not where only whether is needed, includes the awkward and wordy construction has the capability to, and unnecessarily repeats the idea of capability with can.

Choices D and E use unidiomatic constructions where the phrase its ability to broaden is required. Choice B--idiomatic, concise, and correct--is best.

ETS不但不喜歡 whether 後面加一個or not

在whether與if同時在不同選項出現，並且做是否解釋的時候，也是多選whether，少用if

ETS认为whether or not 罗嗦重复，所以必错。