单选题 Can the positive integer n be written as the sum of two different positive prime numbers?(1) n is greater than 3. (2) n is odd.
【正确答案】 E
【答案解析】Determine if the positive integer n can be written as the sum of two different positive prime numbers.(1) It is given that n > 3. If n = 5, then n = 2 + 3 and 2 and 3 are different positive prime numbers. However, n = 11, then n can be written as the following sums of two different positive numbers: 1 + 10,2 + 9, 3 + 8,4 + 7, and 5 + 6. In no case are the addends both prime; NOT sufficient.(2) It is given that n is odd. The values of n in the examples used to show that (1) is not sufficient also satisfy (2); NOT sufficient.Taken together, (1) and (2) are not sufficient because the same examples used to show that (1) is not sufficient also show that (2) is not sufficient.The correct answer is E;both statements together are still not sufficient.