Answer:
D. Sulfonation
Step-by-step explanation:
Electrophilic aromatic substitution -
The subsitution reaction , where the hydrogen atom of an aromatic ring is replaced by an external electrophile .
Sulfonation reaction -
The subsitution reaction , where the hydrogen atom of an aromatic ring ( benzene) is replaced by an sulfonyl group , is called an Sulfonation reaction .
The Sulfonation reaction is reversible in nature , because , heating of aqueous sulfuric acid with sulfonic acid , can lead to a reverse reaction , i.e. , desulfonation .