Among the following, the compound that can be most readily sulphonated is

Solution :
TIPS/FORMULAE :
$$ - N{O_2}, - Cl\,\,{\text{and}}\, - OH$$     are electron-attracting or withdrawing group due to $$ - M, - E\,\,\,{\text{and/or}}\, - I$$     effects where as $$C{H_3}$$  show, $$ + I$$  effect ( electron releasing ).
Because of the $$ + I$$  effect of the $$C{H_3}$$  group, toluene has the highest electron density in the  $$o - $$  and $$p - $$ positions and hence can be most readily sulphonated.