This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition and health, Subject name: Social & Preventive Medicine
[{'content': 'All are trace elements except - \nSelect and explain. \nA. Iron, B. Fluoride, C. Potassium, D. Zinc', 'role': 'user'}, {'content': "Answer: C \nExplanation: Trace elements are elements required by the body in quantities of less than a few milligrams per day.eg.iron,iodine,flourine,zinc,copper cobalt,chromium,manganese,molybdenum,selenium,nickel,tin,silicon and vanadium.(Ref.PARK'S textbbok of sociala and preventive medicine 21st edition page no.573)", 'role': 'assistant'}]