Among the following compounds,the one that undergoes sulfonation most easily is .......

Give the decreasing order of reactivity for the $ESR$ (Electrophilic Substitution Reaction) for the following compounds:
$(1)$ Benzene
$(2)$ Toluene
$(3)$ Chlorobenzene
$(4)$ Nitrobenzene

Which of the following compounds has two different $C-C$ bond lengths?

The correct order of reactivity towards the electrophilic substitution of the compounds aniline $(I)$,benzene $(II)$,and nitrobenzene $(III)$ is

Catalytic hydrogenation of benzene gives

Enumerate different aromatic electrophilic substitution reactions and provide the reactions that show how the electrophiles $(E^{+})$ are formed.