This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition, Subject name: Medicine
Keshan disease is due to deficiency of - 
Select and explain. 
A. Selenium, B. Chromium, C. Copper, D. Manganese
A: Selenium
Answer: A: Selenium 
Explanation: selenium def cause cardiomyopathy in children known as Keshan's disease which is endemic cardiomyopathy Ref Harrison 20th edition pg 99e