This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Secular trend is \nSelect and explain. \nA. Long term, B. Sho term, C. Both, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The term secular trend implies changes in the occurence of diseases (i.e. A progressive increase or decrease)over a long period of time generally several years or decades.(refer pg no: 66 park 23 rd edition)', 'role': 'assistant'}]