$\text{NaOH}$ is base so it will react with acid.
$\text{H}$ which is attached with $\text{-COOH}$ is more acidic due to the stability of conjugate base (equivalent resonating structure). So, b and c is more basic. And in a and b, b is more acidic because it's conjugate base is stabilised due to $-\text{I}$ effect of ${\text{-NO}}_{\text{2}}$