The correct answer is: Cohesion of water is greater than its adhesion with glass.
Water molecules are polar, which means they have a positive end and a negative end. This polarity allows water molecules to form hydrogen bonds with each other. Hydrogen bonds are weak bonds, but they are very numerous, and they give water its unique properties. One of these properties is surface tension, which is the tendency of water to minimize its surface area. This is why water forms droplets, and why it beads up on a waxy surface.
Mercury is a metal, and metals are not polar. This means that mercury molecules do not form hydrogen bonds with each other. As a result, mercury does not have surface tension, and it spreads out to form a thin layer on a glass surface.
Option A is incorrect because mercury is a metal, but this does not explain why it does not spread out on a glass surface.
Option B is incorrect because the density of mercury is greater than that of water, but this does not explain why mercury does not spread out on a glass surface.
Option C is incorrect because the cohesion of mercury is greater than its adhesion with glass, but this does not explain why mercury does not spread out on a glass surface.