If n is any prime number greater than 2, which of the following CANNOT be a prime number?

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问题 If n is any prime number greater than 2, which of the following CANNOT be a prime number?

选项 A、n-4
B、n-3
C、n-1
D、n+2
E、n+5

答案E

解析 若n是任一个大于2的质数,下面哪一项不能是质数?
解:本题的正确答案是(E)。考生在解这类数字规律题时应采用排除法,把选项代入逐个排除。(A)9-4=5;(B)14-3=11,(C)3-1=2,(D)3+2=5,(E)无论如何也得不到质数,因为大于2的质数都是奇数,奇数加5必为大于2的偶数,所以,n+5不可能是质数。
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本试题收录于: GRE QUANTITATIVE题库GRE分类
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