A. calcium hydroxide or magnesium hydroxide
B. calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI)
C. sodium hydroxide or magnesium hydroxide
D. calcium chloride or sodium chloride salts
Correct Answer:
Option B = calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI)
Explanation
Salts of Calcium and Magnesium are responsible for hardness of water. Bicarbonates, Carbonates, Chlorides, and Sulfates of Calcium and Magnesium cause temporary and permanent hardness.