(N/A) Nitration is an electrophilic aromatic substitution reaction where the rate depends on the electron density of the aromatic ring. The nitronium ion $(NO_2^+)$ acts as an electrophile.
$1$. The $-CH_3$ group in toluene is an electron-donating group ($+I$ effect and hyperconjugation),which increases the electron density of the benzene ring,making it more reactive towards electrophilic substitution than benzene.
$2$. The $-NO_2$ group in $m$-dinitrobenzene is a strongly electron-withdrawing group ($-I$ and $-M$ effects),which significantly decreases the electron density of the benzene ring,making it the least reactive.
$3$. Benzene has intermediate reactivity compared to toluene and $m$-dinitrobenzene.
Therefore,toluene undergoes nitration most easily because the methyl group activates the ring towards electrophilic attack.