Which is more stable:
-True solution
-Suspension

Hint: True solution is the solution that has solute particles of size smaller than \[1{\text{ }}nm\] ( \[{10^{ - 9}}\] metres) in diameter, and cannot be seen with naked eyes. A suspension is cloudy and heterogeneous. The particles are larger than the particles of solution and can be seen with naked eyes.

Complete answer:
True solutions are more stable than suspension.
True solutions remain stable as the particles are almost uniform in size and do not settle down if left untouched for a given time interval. The particles mix well with each other, which shows that the elements form stable bonds which is also a sign of overall stability of true solution. On the other hand, the particles involved in suspension do not mix well with each other and also settle down if left untouched for a given time interval.

Additional information:
In true solutions, neither the solute nor the solvent can be distinguished even under a microscope. It does not show Tyndall effect and is clear and transparent. True solutions cannot be separated by filtration as the size of both solute and solvent is very small as compared to the pores of filter paper.
In suspension, the size of particles is more than \[1000{\text{ }}nm\] (\[{10^{ - 6}}\] metres) and can be seen with naked eyes. The particles of suspension, in its suspended form, show the Tyndall effect. Suspension particles can be separated by filtration. Suspension is opaque in nature.

Note:
The Tyndall effect is the phenomenon of scattering of light particles in a colloid or in a very fine suspension. It is also known as Tyndall scattering. The Tyndall effect is seen when light-scattering particulate matter is dispersed in an otherwise light-transmitting medium, when the diameter of an individual particle is the range of roughly between \[40\] and \[900{\text{ }}nm\].