Hi Sri,

This DS question asks "is D negative?" This is a YES/NO question. We know nothing about D.

Fact 1: E + D = -12

It's pretty easy to see that we don't know anything about D. The E could be positive, negative or 0, so the value of D will vary. It might be negative (YES answer), or positive (NO answer) or zero (NO answer.

Fact 1 is INSUFFICIENT

Fact 2: E - D < -12

We run into the same situation here as in Fact 1: the D could be positive, negative or 0.
Fact 2 is INSUFFICIENT.

Combined, we can actually use algebra to quickly prove what's going on.

From Fact 1, we know that E = -12 - D

Substituting that value into the inequality, we get....

(-12 - D) - D < -12
-12 - 2D < -12
-2D < 0
-D < 0
D > 0

Since D is always positive, the answer to the question is ALWAYS NO.
Combined, SUFFICIENT.

Final Answer: C

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