6. No senator spoke1 at the convention unless he or she was a Democrat2. No Democrat both spoke at the convention and was a senator
Which one of the following conclusions can be correctly drawn3 from the statements above?
N one but senators spoke at the convention.
No Democrat spoke at the convention.
only Democrats4 spoke at the convention.
No senator spoke at the convention.
Some Democrat senators spoke at the convention.
答案：D
我完全沒思路這種題該如何做呢？
第一句說明會議上假如有參議員發言的話，他只能是民主黨的參議員，第二句講發言的人要么是民主黨員，要么是參議員。依據第一句，否定掉參議員，只剩民主黨了