This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Social & Preventive Medicine
Which of the following do not cause hardness of water ? 
Select and explain. 
A. Calcium carbonate, B. Calcium sulphate, C. Calcium bicarbonate, D. Magnesium bicarbonate
A: Calcium carbonate
Answer: A: Calcium carbonate 
Explanation: * Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). * Permanent hardness is caused by dissolved calcium sulfate (which is not removed by boiling ref : park 21st ed