Answer: Benzene would act as Catalyst (C6H6)
Explanation:
While alkene undergo an addition reaction when treated with bromine, benzene is inert under the same conditions.
After the electrophilic attack of bromide to the benzene, the hydrogen on the same carbon act as bromine, substitutes the carbocation in which resulted from the attack. Hence, it being an electrophilic aromatic SUBSTITUTION. Benzene serves as our catalyst in the halogenation.
