The correct answer is D. Sugar.
Camphor is a solid at room temperature and does not dissolve in water. Sulphur is also a solid at room temperature and does not dissolve in water. Common salt is a white crystalline solid that dissolves in water. Sugar is a white crystalline solid that dissolves in water.
The solubility of a substance is the amount of that substance that can dissolve in a given amount of solvent at a given temperature. The solubility of a substance depends on the nature of the substance and the nature of the solvent.
Water is a polar solvent, which means that it has a positive end and a negative end. The positive end of the water molecule is attracted to the negative end of the sugar molecule, and the negative end of the water molecule is attracted to the positive end of the sugar molecule. This attraction causes the sugar molecules to dissolve in the water.
Camphor, sulphur, and common salt are all non-polar substances. Non-polar substances do not have a positive end and a negative end, so they are not attracted to water molecules. This is why camphor, sulphur, and common salt do not dissolve in water.