=>

Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember that equal number of variables and independent equations ensures a solution.

The first step of VA(Variable Approach) method is modifying the original condition and the question, and rechecking the number of variables and the number of equations.

Under the condition ab > 0, the question ab2 > 0 is equivalent to a > 0.

The condition 1) is equivalent to the question a > 0. This is sufficient.

And under the original condition ab > 0, the condition 2) b > 0 is equivalent to a > 0. This is sufficient too.

Therefore, the answer is D.

By the tip 1) of VA method, since two conditions are same, we can choose D as the answer.

Ans: D

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare

The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.

"Only $99 for 3 month Online Course"

"Free Resources-30 day online access & Diagnostic Test"

"Unlimited Access to over 120 free video lessons - try it yourself"