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
"Goitre is prevalent at higher altitude", is an example of - 
Select and explain. 
A. Direct association, B. Indirect association, C. Causal association, D. Temporal association
B: Indirect association
Answer: B: Indirect association 
Explanation: Endemic goiter is generally found in high altitude showing thereby an association between altitude and endemic goiter. We know that endemic goiter is not due to altitude but due to environmental deficiency of iodine. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 96