This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Medicine
[{'content': 'In a patient with smoking history, which is important? \nSelect and explain. \nA. Duration of smoking, B. Number of smoking, C. Brand of Cigarette, D. Filter of cigarette', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Duration of smokingThough this is a highly debatable topic most serach results and discussion with faculty and google books (LASLC Textbook of Prevention and Early Detection of Lung Cancer) mention duration of smoking to be more important that the number of cigarettes smoked.', 'role': 'assistant'}]