In the depression of freezing point experiment it is found that:A. Vapour pressure of the solution is less than that of pure solventB. Vapour pressure of the solution is more than that of pure solventC. Only solute molecules solidify at the freezing pointD. Only solvent molecules solidify at the freezing pointA and D onlyB and C onlyA and C onlyA only

The correct answer is A and D only.

Here's why:

A. Vapour pressure of the solution is less than that of pure solvent: This is true. When a non-volatile solute is added to a solvent, it decreases the vapour pressure of the solvent. This is because the solute particles occupy the surface area of the solvent, thereby reducing the number of solvent particles that can escape into the vapour phase.

D. Only solvent molecules solidify at the freezing point: This is also true. The freezing point is the temperature at which a liquid turns into a solid when cooled. In a solution, the solvent is the component that changes state, so it's the solvent molecules that solidify at the freezing point.

B. Vapour pressure of the solution is more than that of pure solvent: This is false. As explained above, the addition of a non-volatile solute to a solvent decreases the vapour pressure of the solvent.

C. Only solute molecules solidify at the freezing point: This is also false. It's the solvent, not the solute, that changes state at the freezing point.