This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Carbonic anhydrase is an example of: 
Select and explain. 
A. Lipoprotein, B. Phosphoprotein, C. Metalloprotein, D. Chromoprotein
C: Metalloprotein
Answer: C: Metalloprotein 
Explanation: Metalloenzymes: 

These enzymes hold the metals rather tightly which are not readily exchanged. e.g., alcohol dehydrogenase, carbonic anhydrase, alkaline phosphatase, carboxypeptidase and aldolase contain zinc.
Phenol oxidase (copper)
Pyruvate oxidase (manganese)
Xanthine oxidase (molybdenum)
Cytochrome oxidase (iron and copper)

Key Concept:
Metalloproteins: They contain metal ions. Examples are Hemoglobin (Iron), Cytochrome (Iron), Tyrosinase (Copper) and Carbonic anhydrase (Zinc).
Ref : Textbook of Biochemistry, Satyanarayana