(B) Set $(ii)$ is an appropriate set of reactants for the preparation of $1-methoxy-4-nitrobenzene$. The reaction is: $p-nitrophenoxide + CH_3Br \rightarrow 1-methoxy-4-nitrobenzene + NaBr$.
In set $(i)$,the reactant is $1-bromo-4-nitrobenzene$. Aryl halides are generally unreactive towards nucleophilic substitution reactions under ordinary conditions because the $C-X$ bond has partial double bond character due to resonance and the $sp^2$ hybridized carbon atom is more electronegative. Furthermore,$CH_3ONa$ is a strong nucleophile and base,but it cannot easily displace the halide from the aryl ring in this manner compared to the Williamson ether synthesis shown in set $(ii)$.