A. Sodium bicarbonate

B. Calcium sulfate

C. Calcium bicarbonate

D. None of these

Detail:

Calcium sulfate is the inorganic compound with the formula CaSO₄ and related hydrates. In the form of γ-anhydrite, it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. Permanent hardness of water is due to the presence of Calcium sulfate. Permanent hardness is hardness (mineral content) that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium sulfate and/or magnesium sulfates in the water, which do not precipitate out as the temperature increases.