Hi pchun008,
I assume that this question involves exponent rules. For future reference, when posting these types of questions, you should use the following notation:
When referring to X-squared, write X^2
When referring to Y-cubed, write Y^3
Etc.
Here, were told that abcd is not equal to 0, so NONE of the variables can be 0.
We're asked if A(B^2)(C^3)(D^4) < 0? This is a YES/NO question.
Since we're not allowed to use 0, we already know that (B^2) is going to be positive and (D^4) is also going to be positive.
This question is ultimately asking "Is A(C^3) < 0?"
This question can further be "re-written" as "Is one of A or C negative?" although you might not need to take this question that far.
Fact 1: A(B^2)(C^3) < 0
Since (B^2) = positive, this Fact tells us that A(C^3) < 0, so the answer to the question is ALWAYS YES.
Fact 1 is SUFFICIENT
Fact 2: (B^2)(C^3)(D^4) < 0
Since (B^2) is positive and (D^4) is positive, this Fact tells us that (C^3) < 0.
However, it does not tell us anything about the value of A.
If A = negative, then the answer to the question is NO.
If A = positive, then the answer to the question is YES.
Fact 2 is INSUFFICIENT
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
