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': 'Which of the following is true about Secular trend - \nSelect and explain. \nA. Road side accident is a good example, B. Due to environmental factors, C. Is due to normally occuring variation in herd immunity, D. Consistent change in a paicular direction over a period of time', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Consistent change in a paicular direction over a period of time The term 'Secular trend' implies changes in the occurrence of disease i.e. a progressive increase or decrease in incidence over a long period of time, such as several years or decades.", 'role': 'assistant'}]