Concept:A stable solution maintains uniform composition and does not allow solute particles to settle over time.
Explanation:The correct definition for a stable solution is that the solute particles do not settle down when left undisturbed.
In a true solution, solute particles are dissolved at the molecular or ionic level, forming a single homogeneous phase.
This uniformity persists indefinitely as long as external conditions (temperature, pressure) remain constant.
Option A is wrong because floating particles on the surface indicate incomplete dissolution, making the mixture unstable.
Option B describes a suspension, where solute particles are large and settle due to gravity.
Option C describes immiscible liquids (e.g., oil and water) that form separate layers, not a stable solution.
Stable solutions, like salt in water or sugar in water, are transparent and consistent throughout.
They exhibit no settling, no separate layer, and no floating of particles.
Answer:The solute particles do not settle down when left undisturbed. (Option D)