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': 'What do you understand by the term secular trend- \nSelect and explain. \nA. Long term changes, B. Sho long term changes, C. Seasonal Changes, D. Periodical changes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The term secular trend implies changes in the occurrence of disease(i.e. A progressive increase or decrease)over a long period of time, generally several years or decade. (refer pg no:66 park textbook 23 rd edition)', 'role': 'assistant'}]