The solution of the differential equation $\frac{dy}{dx} - \frac{2xy}{1+x^2}=0$ is :

Question

( A ) $y = A\sqrt{1+x^2}$
( B ) $Y = \frac{A}{\sqrt{1+x^2}}$
( C ) $Y = \frac{A}{(1+x^2)}$
( D ) $y = A (1+x^2)$