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': 'Post zone phenomenon is due to \nSelect and explain. \nA. Antigen excess, B. Antibody excess, C. Haptens, D. Equal Antigen & Antibody', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Prozone - Antibodies are excess.\nPostzone - Antigen excess.', 'role': 'assistant'}]