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: Social & Preventive Medicine
[{'content': 'Secular trend is a - \nSelect and explain. \nA. Long term, B. Sho term, C. Both, D. None', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Long term", 'role': 'assistant'}]