What is the default subnet mask for a Class C network?

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

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

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

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

Which of the following can operate at both layers $2$ and $3$ of the OSI model?

Bridge

Switch

Repeater

Hub