Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?

Nitration of benzene is an electrophilic substitution reaction. Presence of electron releasing group such as —$CH_{ 3 }$ activates the benzene nucleus towards electrophilic substitution while presence of electron withdrawing group such as —$NO_{ 2 }$ deactivates the benzene nucleus towards electrophilic substitution. Therefore, the ease of nitration decreases in the order
Toluene > benzene > m-dinitrobenzene
Thus, toluene will undergo nitration most easily.