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: Microbiology
[{'content': 'Catalase positive, beta-hemolytic staphylococcus - \nSelect and explain. \nA. S. aureus, B. S. epidermidis, C. S. saprophyticus, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: All staphylococci are catalase positive.\nAmongst staphylococci, staph. aureus is beta-hemolytic.\nMost species of coagulase-negative staphylococcus species are non-hemolytic.', 'role': 'assistant'}]