Put water in it and the salt will dissolve and the sand will stay at the bottom
6.02*10^23 is Avagadro's number representing the number of molecules per mole of substance.
The correct answer is B. The magnifying lens is a converging lens. It focuses the incoming light to one single point. It can be proved when you use the magnifying glass to burn a piece of paper. You can observe that the light will concentrate at a single point.
