If $$y = \tan^{-1}\frac{2x}{1 - x^2}$$, then $$\frac{dy}{dx}$$ is

A

$$\frac{2}{1 + x^2}$$

B

$$\frac{2}{1 - x^2}$$

C

$$\frac{1}{1 + x^2}$$

D

$$\frac{2x}{\sqrt{1 + x^2}}$$