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
All of the following statements about Hardness of Water are true, except:(2018) 
Select and explain. 
A. Hardness is soap destroying power of water, B. Bicarbonates cause Permanent Hardness, C. Carbonate hardness can be removed by boiling, D. Hardness is mainly caused by Calcium and Magnesium salts
B: Bicarbonates cause Permanent Hardness
Answer: B: Bicarbonates cause Permanent Hardness 
Explanation: Hardness may be defined as the soap destroying power of water. Hardness in water is caused mainly by four dissolved compounds. These are (1) Calcium bicarbonate (2) Magnesium bicarbonate (3) Calcium sulphate, and (4) Magnesium sulphate. The presence of any one of these compounds produces hardness. There are others which are of less impoance. Chlorides and nitrates of calcium and magnesium can also cause hardness but they occur generally in small amounts. Hardness is classified as carbonate and non-carbonate. The carbonate hardness which was formerly designated as "temporary" hardness is due to the presence of calcium and magnesium bicarbonates. The non-carbonate hardness formerly designated as "permanent" hardness, is due to calcium and magnesium sulphates, chlorides and nitrates Ref:- park;pg num:- 786