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': 'Antigen - Antibody reactions occurs at its best at \nSelect and explain. \nA. Prozone, B. Postzone, C. Zone of equivalence, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Zone of equivalence - Ag and Ab level equal thus, best.', 'role': 'assistant'}]