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': 'Gram positive, catalase negative cocci ? \nSelect and explain. \nA. Staph aureus, B. Staph epidermidis, C. Staph saprophyticus, D. Pneumococcus', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Pneumococcus", 'role': 'assistant'}]