This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
Co factor of glutathione peroxidase - 
Select and explain. 
A. Selenium, B. Magnesium, C. Manganese, D. Zinc
A: Selenium
Answer: A: Selenium 
Explanation: Ans. is 'a' i.e., Selenium* Keshan's disease is a form of cardiomyopathy and is characterized by multifocal myocardial necrosis, cardiac arrhythmias and cardiac enlargement.* It is prevalent in the Keshan province of China, soil of which is deficient in Selenium.* Selenium deficiency in the soil is found to cause an increased prevalence of highly cirulent coxsackie B virus. Hence selenium deficiency and the superimposed Coxsackie B virus is found to precipitate Keshan's disease.* Treatment is selenium and Vitamin E supplementation