^^ this is the exact rationale. This problem has 2 main components. 1) It's an infinite set always increasing by 2, and 2) You can only assume that -1 is the lowest number since it's a MUST question. Starting with -1 yields the narrowest choice, and D is thus, as egybs said, unambiguously correct.egybs wrote:Wow.. blast from the past! As I said a year and a half ago, before I scored 99th percentile on the gmat, the answer is unambiguously D. In case the old posts are enough of an explanation here it goes again:
The set is going to be infinitely long and will continue increasing positively. Any number that's in the set will also have the same number + 2 (t+2). So if we know that 4 is in the set, 6, 8, 10,12, 14, 16, 18,20, etc, etc, etc are also definitely there.
So if we know that -1 is in the set, we know with certainty that 1,3,5,7,etc are also in the set.
What we don't know is where the trend starts. -1 could be the lowest number, but it could also be -3, or -5, or even -4.. we just don't know where it starts. Therefore, the only thing we can conclude with certainty is that -1,1,3,5,7,9, etc are in the set. So the answer is, once again, unambiguously, D.
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