The correct option is A Ca(HCO3)2
Permanent hardness is due to the presence of dissolved chlorides and sulphates of Calcium, Magnesium, Iron, and other heavy elements.
Temporary hardness is caused by bicarbonates of Calcium and Magnesium.
Thus, Ca(HCO3)2 and Mg(HCO3)2 is responsible for temporary hardness of water.