The solution of $x^2 +y^2 \frac{dy}{dx}=4$ is :

Question

( A ) $x^3+y^3 =12x +c$
( B ) $x^2 +y^2 = 8x +c$
( C ) $x^3 +y^3 = 12x +c$
( D ) $x^2+y^2 =8x +c$