which subnet masks would be valid for a subnetted class b address

$255\mathrm{.}254\mathrm{.}0\mathrm{.}0$

$255\mathrm{.}224\mathrm{.}0\mathrm{.}0$

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

$255\mathrm{.}255\mathrm{.}252\mathrm{.}0$