Another way of looking at the problem can be
X^2 > X means two things
1) X cannot be a fraction.
2) X can be a negative no.
Once it is ensured that X is non Negative number (as done by option A)
it will ensue that X^3 > X^2.
I Hope it helps
"The way to succeed is to double your error rate."
"Most people who succeed in the face of seemingly impossible conditions are people who simply don't know how to quit."