[求助]LAST-10-4-4 纯逻辑推理

藕昏了NOW, ONLY IF A + B 成立， THEN C 成立. 等价命题是什么？如下题：参考答案是C.

4. Only if the electorate is moral and intelligent will a democracy function well.

Which one of the following can be logically inferred from the claim above?

(A) If the electorate is moral and intelligent, then a democracy will function well.

(B) Either a democracy does not function well or else the electorate is not moral or not intelligent.

(C) If the electorate is not moral or not intelligent, then a democracy will not function well.

(D) If a democracy does not function well, then the electorate is not moral or not intelligent.

(E) It cannot, at the same time, be true that the electorate is moral and intelligent and that a democracy will not function well.

ONLY IF A and B 成立， THEN C。即C-----〉A and B。逆否命题为：非A or 非B----->非C。

答案C 为逆否命题