. No senator spoke at the convention unless he or she was a Democrat. No Democrat both spoke at the convention and was a senator
Which one of the following conclusions can be correctly drawn from the statements above?
(A) N one but senators spoke at the convention.
(B) No Democrat spoke at the convention.
(C) Only Democrats spoke at the convention.
(D) No senator spoke at the convention.
(E) Some Democrat senators spoke at the convention
此题选d，我倒是能明白，但对它的推导总不清楚，请牛人指导一下。
