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: Pharmacology
[{'content': 'Diphenhydramine used as antitussive is a \nSelect and explain. \nA. Central opioid agonist, B. NMDA blocker, C. Antihistamine, D. Mucolytic', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Diphenhydramine is an anti histamine used for mild cough.', 'role': 'assistant'}]