Zinc is a cofactor for which of the following enzymes?: (A) Hexokinase, (B) Cytochrome coxidase, (C) Carbonic anhydrase, (D) Xanthine oxidase
Answer is C. Zinc acts as cofactor for many enzymes :

Carbonic anhydrase
Alcohol dehydrogenase
Alkaline phosphatase
Lactate dehydrogenase
ALA dehydratase
Carboxypeptidase.