The solution of $x \; dx + y \;dy = x^2y\; dy - xy^2\;dx$ is :

Question

( A ) $x^2+1=c(1-y^2)$
( B ) $x^2 -1 = c (1+y^2)$
( C ) $x^2+1 = c(1-y^2)$
( D ) $x^2 -1 = c (1-y^2)$