Find the solution of $\Large \frac{dy}{dx}\normalsize =2^{y-x}.$

Question

$\begin{array}{1 1}(A)\; 2^{-y}-2^{-x}=c \\ (B)\; 2^{-y}+2^{-x}=c \\ (C)\; 2^{y}+2^{x}=c \\(D)\; 2^{-x}-2^{y}=c \end{array} $