The correct choice is (c) Epimerases
For explanation I would say: Isomerases involves the catalysis of isomerization reaction. Isomerase includes epimerase, racemase and intramolecular transferase. Hence Epimerase belongs to isomerase class of enzymes. Aldolase belongs to lyases whereas oxygenases belongs to oxidoreductases. Esterases belong to the hydrolases class of enzymes.