This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diabetes Mellitus, Subject name: Medicine
Glucose intolerance is caused by the deficiency of? 
Select and explain. 
A. Selenium, B. Magnesium, C. Chromium, D. Zinc
C: Chromium
Answer: C: Chromium 
Explanation: Chromium acts as a cofactor for insulin at insulin receptors and dietary deficiency of chromium would thus lead to impaired glucose tolerance.