The correct answer is (a). Water is a polar molecule, which means that it has a positive end and a negative end. This polarity allows water molecules to form hydrogen bonds with other water molecules and with other polar molecules. Hydrogen bonds are weak bonds, but they are very numerous in water. This makes water a very good solvent, and it can dissolve many different substances.
(b) Water is a good conductor of heat, but this is not the reason why it can dissolve more substances than any other liquid.
(c) Water has a high value of specific heat, which means that it takes a lot of energy to raise the temperature of water. This is not the reason why water can dissolve more substances than any other liquid.
(d) Water is an oxide of hydrogen, but this is not the reason why it can dissolve more substances than any other liquid.