Which of the following differential equations has $y\;=\;c_1e^x+c_2e^{-x}$ as the general solution?

Question

$$(A)\;\frac{d^2y}{dx^2}+y=0\quad(B)\;\frac{d^2y}{dx^2}-y=0\quad(C)\;\frac{d^2y}{dx^2}+1=0\quad(D)\;\frac{d^2y}{dx^2}-1=0$$