The following command has been configured on a Cisco switch:

Switch$($config$)$# ip routing Which command is required to forward unknown unicast traffic to router $10\mathrm{.}1\mathrm{.}1\mathrm{.}1?$

a$)$ ip default$-$gateway $10\mathrm{.}1\mathrm{.}1\mathrm{.}1$

b$)$ default$-$gateway $10\mathrm{.}1\mathrm{.}1\mathrm{.}1$

c$)$ ip route $0\mathrm{.}0\mathrm{.}0\mathrm{.}0/010\mathrm{.}1\mathrm{.}1\mathrm{.}1$

d$)$ ip route $0\mathrm{.}0\mathrm{.}0\mathrm{.}00\mathrm{.}0\mathrm{.}0\mathrm{.}010\mathrm{.}1\mathrm{.}1\mathrm{.}1$

e$)$ gateway$-$last$-$resort $10\mathrm{.}1\mathrm{.}1\mathrm{.}1$