Which of the following has the lowest heat of combustion?

The number of $\pi$-bonds and lone pair$(s)$ present in the major benzenoid product,which is formed when benzene reacts with acetyl chloride in the presence of anhydrous aluminium chloride,are respectively:

Given the following structures:
$(I)$ $1,3,5-$trimethylbenzene (mesitylene)
$(II)$ $1,3-$dimethyl$-5-$methylenecyclohexa$-1,3-$diene
$(III)$ $1,3,5-$trimethylenecyclohexane
The enthalpy of hydrogenation of these compounds will be in the order as:

Which of the following is not used in the Friedel-Crafts reaction?

Benzene on treatment with a mixture of conc. $HNO_3$ and conc. $H_2SO_4$ at $100 \ ^oC$ gives

Arrange the following compounds in decreasing order of their reactivity towards electrophilic substitution $(E^{+})$:
$C_6H_5NH_2$,$C_6H_5NHCOCH_3$,$C_6H_6$,$C_6H_5SO_3H$