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题库 / Prep2007E2-DS-29
Is the positive integer n odd?
(1) n = 2k + 1, where k is a positive integer.
(2) 2n + 1 is an odd integer.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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奇数/偶数*2+1均等于奇数，所以B不对。对策：应排除反例后再下结论。
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