This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'What is the ideal hardness of drinking water in mEg/Litre? \nSelect and explain. \nA. >3, B. <1, C. 3-Jan, D. >6', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Drinking water should be moderately hard. Softening of water is recommended when the hardness exceeds 3 mEq/L (300 mg per litre).', 'role': 'assistant'}]