Within a classful addressing, $\_\_\_\_$ is the default subnet mask for a Class C address.

$255\mathrm{.}0\mathrm{.}0\mathrm{.}0$

$255\mathrm{.}255\mathrm{.}0\mathrm{.}0$

$255\mathrm{.}255\mathrm{.}255\mathrm{.}0$

$255\mathrm{.}255\mathrm{.}255\mathrm{.}255$