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': 'Prozone phenomenon is due to- \nSelect and explain. \nA. Excess antigen, B. Excess antibody, C. Hyperimmune reaction, D. all', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Excess antibody", 'role': 'assistant'}]