UPSC 2015 CDS I GK Paper

When hard water is evaporated completely, the white solid remains in the container. It may be due to the presence of all the three substances (given in the form of three options in the question) or, we can say, salts of Ca and Mg. They are:
1. Carbonates of Ca and Mg
2. Sulphates of Ca and Mg
3. Chlorides of Ca and Mg