`x^2+y^2=r^2` is a solution of `y=x dy/dx+r sqrt(1+(dy/dx)^2)`

Options

A. (a) `y=x dy/dx+r sqrt(1+(dy/dx)^2)`
B. (b) `y=xsqrt(1+(dy/dx)^2)+r^2y`
C. (c) `d^2y/dx^2+x dy/dx-y=0`
D. (d) `frac{d^2y}{dx^2}+(x+1)dy/dx=0`