$\begin{array}{1 1}(A)xyy'' + x(y')^2 - y' = 0 \\(B)xyy'' - x(y')^2 - yy' = 0 \\(C)xyy'' + x(y')^2 + yy' = 0 \\ (D)xyy'' + x(y')^2 - yy' = 0 \end{array} $