Which phenomenon occurs when a system at equilibrium is disturbed?

When a system at equilibrium is disturbed, it responds in a manner that seeks to restore a new state of equilibrium. This behavior is described by Le Chatelier's Principle, which states that if an external stress is applied to a system at equilibrium, the system will adjust to counteract that stress and alleviate the change.

For instance, if the concentration of a reactant in a chemical reaction at equilibrium is increased, the system will shift towards the products to reduce the concentration of that reactant back to a balanced state. This adjustment ensures that the system can accommodate the disturbance and establish a new equilibrium condition, either by altering concentrations, pressure, or temperature depending on the nature of the disturbance.

This dynamic response is crucial for maintaining chemical processes and biological systems where equilibrium plays an essential role in stability and function. Thus, the correct answer reflects a fundamental principle in chemistry regarding equilibrium systems and their inherent ability to adapt to changes.