Power Rule for Integration

I. $\int x^{-3}\,dx = -\frac{1}{2*x^2} + C$

II. $\int x^{-3}\,dx = -\frac{1}{3*x^3} + C$

III. $\int x^{-3}\,dx = \frac{1}{2*x^2} + C$

Which of the following statements is true?