$1.$ Describe which one is correct expression to filter out all the packets not containing IP address $1\mathrm{.}2\mathrm{.}3\mathrm{.}4$

a$.$ ip$.$addr $!=1\mathrm{.}2\mathrm{.}3\mathrm{.}4$

b$.!($ip$.$addr $==1\mathrm{.}2\mathrm{.}3\mathrm{.}4)$