What is the classful subnet mask for a Class C IPv$4$ Address?

Choose one $*1$ point

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

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

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

$192\mathrm{.}168\mathrm{.}0\mathrm{.}0$