Form a differential equation representing the given family of curves by eliminating arbitrary constants a and b $\large\frac{x}{a}+\frac{y}{b}=1$

Question

$\begin{array}{1 1} (A)\;y'' = 0 \\(B)\;y' = 0 \\ (C)\;xy'' = 0 \\ (D)\;y''' = 0 \end{array} $