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': 'First chemical barrier encountered by microorganism for common exposed sites - \nSelect and explain. \nA. Lysozyme, B. Acidic pH, C. Skin, D. Lactose', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]