Mark (√) against the correct answer in the following: The solution of the D E \frac{d y}{d x}=\frac{\left(1+y^{2}\right)}{\left(1+x^{2}\right)} is.
A. (y+x)=\mathrm{C}(1-y x)
B. (y-x)=\mathrm{C}(1+y x)
C. y=(1+x) \mathrm{C}
D. None of these