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
Secular trend means - 
Select and explain. 
A. Seasonal changes, B. Periodical changes, C. Religion changes, D. Long term changes
D: Long term changes
Answer: D: Long term changes 
Explanation: Long term or secular trends 

The term secular trend implies changes in the occurrence of disease over a long period of time, generally several years or decades.
There may be progressive increase or decrease in the occurrence of disease.

Examples -

CHD, lung cancer, and DM have shown a consistent upward trend in developed countries.
TB, typhoid fever, diphtheria and polio have shown a declined trend in developed countries.