(c)
Given, ellipse $\frac{x^{2}}{16} + \frac{y^{2}}{7} = 1$
$\therefore\ \ e_{1} = \sqrt{1 - \frac{7}{16}} = \frac{3}{4}$
and hyperbola $\frac{x^{2}}{9} - \frac{y^{2}}{7} = 1$
$\therefore\ \ e_{2} = \sqrt{1 + \frac{7}{9}} = \frac{4}{3}$
Now, $e_{1} + e_{2} = \frac{3}{4} + \frac{4}{3} = \frac{25}{12}$