A is:

This is Kolbe’s Electrolysis. It involves the decarboxylation of potassium salts of carboxylic acids at the anode to form hydrocarbons.

Mechanism:

Decarboxylation: The two $$-COOK$$ groups at the 1 and 4 positions are removed as two molecules of $$CO_2$$.

Radical Formation: This generates free radicals at the C1 and C4 positions of the dihydronaphthalene ring.

Aromatization: The 1,4-diradical system undergoes immediate aromatization to reach the most stable state.

Final product: The loss of the carboxyl groups and the resulting electronic rearrangement converts the 1,4-dihydronaphthalene core into a fully aromatic Naphthalene ring.