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: Orthopaedics
[{'content': 'Septic arthritis in a 2 year old child is often caused by- \nSelect and explain. \nA. Hemophilous influenzae, B. Staphylococcus aureus, C. Gonococci, D. Pneumococci', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Staphylococcus aureus is the most common cause of septic arthritis in all ages.', 'role': 'assistant'}]