The inflection point has two conditions: one is that the second derivative is zero, and the other is that the second derivative sign is near the two sides of the point. Find the second derivative of each option separately, leaving out A and B..

C Its second derivative is the second derivative of12 * x. Although the second derivative of point (0,0) is zero, it is obvious that the sign of the second derivative is the same near both sides of this point, so this point is not its inflection point, and so is D.