This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
Obligatory anaerobes cannot withstand oxygen because of absence - 
Select and explain. 
A. Superoxide dismutase, B. Catalase, C. Peroxidase, D. Cytochrome oxidase
B: Catalase
Answer: B: Catalase 
Explanation: Obligate anaerobes may even die on exposure to oxygen. The reason for the apparent toxicity of oxygen for anaerobic bacteria is not well understood. It has been suggested that in the presence of oxygen, hydrogen peroxide and other toxic peroxides accumulate . The enzyme catalase which splits hydrogen peroxide is present in most of the aerobic bacteria but which is absent in anaerobes Ref Ananthanarayan & paniker's Textbook of Microbiology 9th edition pg no:24