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': 'Which antibody has maximum concentration in GI secretions \nSelect and explain. \nA. IgG, B. IgM, C. IgA, D. IgD', 'role': 'user'}, {'content': 'Answer: C \nExplanation: IgA antibody\n\nIt is the second most abundant antibody (after IgG).\nIt is major immunoglubulin in clostrum, saliva, tears, respiratory and gastrointestinal secretions.\nIgA occurs in two forms.', 'role': 'assistant'}]