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': 'Hardness of water has a beneficial which one of the following \nSelect and explain. \nA. Renal diseases, B. Metabolic diseases, C. Cerebrovascular diseases, D. Cardiovascular diseases', 'role': 'user'}, {'content': 'Answer: D \nExplanation: "Hardness of water appears to have a beneficial effect against cardiovascular disease" - Park 621', 'role': 'assistant'}]