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
Habrdness of water has a beneficial effect againts which one of the following - 
Select and explain. 
A. Renal diseases, B. Metabolic diseases, C. Cerebrovascular diseases, D. Cardiovascular diseases
D: Cardiovascular diseases
Answer: D: Cardiovascular diseases 
Explanation: Repos from several countries have shown an inverse statistical association between the hardness of drinking water and the death rate from cardiovascular diseases. Areas supplied with soft drinking water showed a significantly higher prevalence of either aeriosclerotic disease or degenerative hea disease, hypeension, the sudden death of cardiovascular origin. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 787