$\begin{array}{1 1}(A)\;\large\frac{d^2y}{dx^2}=\frac{dy}{dx} \\(B)\;\large\frac{d^2y}{dx^2}-y=0 \\(C)\;\large\frac{d^2y}{dx^2}=0 \\ (D)\;\large\frac{d^2y}{dx^2}-\frac{dy}{dx}-y=0\end{array} $
