This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Water, Subject name: Social & Preventive Medicine
[{'content': 'Most undesirable metal in drinking water is: \nSelect and explain. \nA. Iron, B. Copper, C. Zinc, D. Lead', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Undesirable metal in drinking water: iron, manganese, zinc, copper, aluminum, lead MOST undesirable metal in drinking water: Lead. Lead was earlier seen in drinking water when water was being supplied through lead pipes. Undesirable salts in drinking water: chloride, fluorides, nitrites, nitrates, calcium, magnesium. Undesirable gases in drinking water: ammonia, hydrogen sulphide, methane.', 'role': 'assistant'}]