When a salt is added to its saturated solution, the salt

Analyze the question: We are asked what happens when extra salt (solute) is added to a solution that is already saturated at a given temperature.

Concept: A saturated solution holds the maximum amount of solute it can dissolve at that temperature. It is in dynamic equilibrium:

solute (undissolved) ⇌ solute (dissolved)

The rate of dissolving equals the rate of crystallisation. Adding more salt does not shift the concentration, because the solution cannot take in any more solute.

Solution:

• The added salt cannot dissolve to any extra degree, so it stays as undissolved solid (it settles at the bottom, which is the "precipitate" in this loose sense).
• The concentration of the solution stays the same, so the solution remains saturated and unchanged.

Checking the options:

• A. Wrong. Supersaturation needs a heated solution to be cooled carefully, not just adding more salt.
• B. Wrong. The solution cannot become unsaturated by adding more solute.
• C. Correct. The extra salt does not dissolve and settles out, and the solution's concentration remains unchanged.
• D. Wrong. The salt does not dissolve, and crystals are not formed from the addition itself.

Tip: Think "saturated = full". If a bus is already full, extra passengers cannot get in, and they just stay outside while the bus stays the same. Adding solute to a saturated solution leaves the solution unchanged, and the excess just sits there.