What aggregate address and mask is used for a default route in IPv$4?$

$0\mathrm{.}0.\frac{0\mathrm{.}0}{32}$

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

$255\mathrm{.}255.\frac{255\mathrm{.}255}{32}$

$0\mathrm{.}0.\frac{0\mathrm{.}0}{0}$