The addition of mercuric iodide to an aqueous solution of potassium iodide can have an impact on the freezing and boiling points of the solution. Let's break down the answer and explain each point in detail.

Freezing Point:
When a solute is added to a solvent, it can affect the freezing point of the solution. In this case, mercuric iodide is added to the aqueous solution of potassium iodide.

- The presence of a solute generally lowers the freezing point of a solvent. This phenomenon is known as freezing point depression.
- The addition of mercuric iodide to the solution will increase the number of particles in the solution, which leads to a lower freezing point.
- Therefore, the freezing point of the solution is lowered when mercuric iodide is added.

Boiling Point:
Similar to the freezing point, the addition of a solute can also affect the boiling point of a solution.

- When a solute is added to a solvent, it results in an increase in the boiling point of the solution. This phenomenon is known as boiling point elevation.
- The mercuric iodide added to the aqueous solution of potassium iodide will increase the concentration of particles in the solution, leading to a higher boiling point.
- Therefore, the boiling point of the solution is raised when mercuric iodide is added.

Explanation:
The correct answer for the impact of adding mercuric iodide to an aqueous solution of potassium iodide is options A and D, which state that the freezing point is raised and the boiling point is lowered.

- The addition of mercuric iodide increases the concentration of particles in the solution, causing a decrease in the freezing point and an increase in the boiling point.
- This behavior can be explained by the colligative properties of solutions, which depend on the number of solute particles present in the solution rather than their nature.
- The presence of more particles in the solution disrupts the orderly arrangement of solvent molecules during freezing, resulting in a lower freezing point.
- Similarly, during boiling, the increased number of solute particles requires more energy to break the intermolecular forces and reach the boiling point, leading to a higher boiling point.

In conclusion, when mercuric iodide is added to an aqueous solution of potassium iodide, the freezing point is raised, and the boiling point is lowered, due to the colligative properties of the solution.