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
An example of a preventive antioxidant is: 
Select and explain. 
A. Catalase, B. Tocopherol, C. Superoxide dismutase, D. Urate
A: Catalase
Answer: A: Catalase 
Explanation: Antioxidants fall into two classes:

Preventive antioxidants, which reduce the rate of chain initiation.  ex: Catalase and other peroxidases such as glutathione peroxidase.
Chain-breaking antioxidants, which interfere with chain propagation.  ex: Superoxide Dismutase, Uric Acid, Vitamin E (Most powerful).

Key Concept:
Catalase falls into preventive anti-oxidants which reduce the rate of chain initiation.
Ref : Harper’s illustrated biochemistry, 31st edition.