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': 'The long acting classical H1 antihistaminic include which of the following ? \nSelect and explain. \nA. Chlorpheniramine, B. Astemizole, C. Cetirizine, D. Clemastine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]