This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Hardness of drinking water should be? \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 if hardness ecxeeds 3mEq/l. Soft water- <1 mEq/l Moderately hard- 1-3 mEq/l Hard water- 3-6mEq/l Very hard water- >6mEq/l Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 727', 'role': 'assistant'}]