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': 'Temporary and permanent hardness of water is removed by - \nSelect and explain. \nA. Boiling, B. Addition of lime, C. Permutit method, D. All', 'role': 'user'}, {'content': "Answer: C \nExplanation: REMOVAL OF HARDNESS: Temporary hardness: Boiling Addition of lime Addition of sodium carbonate Permutit process (Na2 Al2 SiO2 H2O) Permanent hardness: Addition of sodium carbonate Base exchange process (permutit process) Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 787", 'role': 'assistant'}]