B. A reaction at equilibrium will respond to balance a change.
Explanation:
The Le Chatelier's principle states that a reaction will respond to balance a change. This is true for a reaction in chemical equilibrium.
Le Chatelier's principle sates that "if any conditions of a system in equilibrium is changed, the system will adjust itself in order to annul the effect of the change".
It explains the effect of applying stress on any system in equilibrium.
The changing conditions are usually concentration, temperature and pressure.
If the stress due to any of them is applied to a system in equilibrium, the equilibrium will respond in the directions which counteracts the effect of the stress.
