is n an odd integer?
1) n is divisible by 3
2) 2n is divisible by twice as many positive integers as n
the key is B.
用举例法, n=3 2n=6 则n是奇数。 n=6 2n=12 n 有4个因子,而12有8个因子,则n为偶数。
即使加上条件一,仍然不能推出,难道不应该是e么?
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