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
What do you understand by the term secular trend ? 
Select and explain. 
A. Long term changes, B. Sho long term changes, C. Seasonal changes, D. Periodical changes
A: Long term changes
Answer: A: Long term changes 
Explanation: Ans. is 'a' i.e., Long term changes