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: Unknown
[{'content': 'Hardness of water occurs due to the presence of all of the following except: \nSelect and explain. \nA. Calcium bicarbonate, B. Magnesium bicarbonate, C. Calcium sulfate, D. Magenesium Oxide', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ref. Foundations of Community medicine. Page. 46\n\xa0\nHardness of water:\n\nTemporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). \u2028\nPermanent hardness is caused by dissolved calcium sulfate (which is not removed by boiling).', 'role': 'assistant'}]