Official Solution:Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question.

Modifying the question:

\(x^3 - x^2 + x < 0\)

⇔ \(x(x^2 - x + 1) < 0\)

⇔ \(x < 0\) since \(x^2 - x + 1 > 0\) always.

So, the question becomes, 'is \(x < 0?\)'.

Condition 1) is certainly sufficient.

Condition 2), \(x^5 + x < 0\), is equivalent to \(x(x^4 + 1) < 0\) or \(x < 0\), since \(x^4 + 1 > 0\) is always true. So, condition 2) is also sufficient.

Therefore, D is the answer.

Answer: 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"