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: Medicine
Hypothyroidism in sub-Himalayan is due to? 
Select and explain. 
A. Iron, B. Iodine, C. Copper, D. Selenium
B: Iodine
Answer: B: Iodine 
Explanation: "Iodine deficiency in sub-Himalayan terrain leads to endemic goitre and hypothyroidism”