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: Pathology
[{'content': 'Which of the following Immunoglobulin protects the body surface: \nSelect and explain. \nA. IgD, B. IgG, C. IgA, D. IgM', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]