Hardness of water may be temporary or permanent. Permanent hardness is due to the presence of
(i) Chlorides of Ca and Mg in water
(ii) Sulphates of Ca and Mg in water
(iii) Hydrogen carbonates of Ca and Mg in water
(iv) Carbonates of alkali metals in water
The answer is the option (i) and (ii) Chlorides of Ca and Mg in water and sulphate of Ca and Mg in water.
Two salts of calcium and magnesium when found as compounds of carbonate, chloride and sulphate dissolve in the water and make it hard.