Hi GmatGreen,

This DS question is built around a few Number Properties. Whether you know the Number Properties already or not, you CAN figure then out as you work through the question. We're told that X is an integer. We're asked "is X|X| < 2^X?" This is a YES/NO question.

Fact 1: X < 0

This means that X is NEGATIVE. Plugging any negative value into the given question, we'd have:

X|X| vs. 2^X
Neg|Neg| vs. 2^Neg
Neg(Pos) vs. Pos
Neg. vs. Pos

So X|X| will always be negative and 2^X will always be positive. This means that the answer to the question will ALWAYS be YES.
Fact 1 is SUFFICIENT

Fact 2: X = -10
With this one value, we COULD plug in -10 to the given question and then answer it. There would be just one answer.
Fact 2 is SUFFICIENT

Final Answer: D

GMAT assassins aren't born, they're made,
Rich