The arenium ion which is not involved in the bromination of Aniline is

Arenium ion: A carbocation formed by electrophilic attack on an aromatic ring, it is a reactive intermediate in electrophilic aromatic substitution. The formation of an arenium ion takes place by electrophilic attack on benzene.

As the delocalisation of electrons stops at an ${\mathrm{sp}}^3$ hybridized carbon atom, the arenium ion is not aromatic in nature. 

Since $-\ddot{\mathrm{N}}{\mathrm{H}}_2$ group is $\mathrm{o}/\mathrm{p}$ directing hence arenium ion will not be formed by attack at meta position i.e.

Hence, the answer is C.