单选题 Efficiency and redundancy are contradictory characteristics of linguistic systems; however, they can be used together to achieve usefulness and reliability in communication. If a spoken language is completely efficient, then every possible permutation of its basic language rounds can be an understandable word. However, if the human auditory system is an imperfect receptor of sounds, then it is not true that every possible permutation of a spoken language's basic language sounds can be an understandable word.
If all of the statements above are true, which one of the following must also be true?

A、 Efficiency causes a spoken language to be useful and redundancy causes it to be reliable.
B、 Neither efficiency nor redundancy can be completely achieved in spoken language.
C、 If a spoken language were completely redundant, then it could not be useful.
D、 If the human auditory system were a perfect receptor of sounds, then every permutation of language sounds would be an understandable word.
E、 (E) If the human auditory system is an imperfect receptor of sounds, then a spoken language cannot be completely efficient.

【正确答案】 E

【答案解析】[解析] 本题为“逆否命题”类型的归纳题。如果某一种口语非常地有效，那么它的每一个基本音素的所有可能排列都能组成一个可被理解的单词的逆否命题为：如果某一种口语的每一个基本音素的所有可能排列不可能都能构成一个可被理解的单词，那么它就不可能非常地有效。根据此逆否命题，再根据本题论述中的最后一句话就可推出如果人类的听觉系统不是一个完善的听觉接受器，那么口语就不可能非常地有效，也即(E)为正确答案；(D)是迷惑选项，但是应当注意到(D)是本题论证中最后一句话的否命题，我们知道原命题正确，否命题不一定正确，所以(D)不是最佳答案；(A)、(B)和(C)都不能从本题的论证中合理地推出。