Correct Answer - B
Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium
`Ca(HCO_(3))_(2)+Ca(OH)_(2)to2CaCO_(3)+2H_(2)O`
The temporary hardness of water can be removed by the addition of calculated quantity of milk of limne which converts soluble bicarbonates into insoluble carnonates which can be removed.