Which of the answer choices correctly describes le châtlier's principle?

a. when a reaction is at chemical equilibrium, a change in the system will cause the system to shift in the direction that will balance the change and the reaction regain chemical equilibrium.

b. when a reaction is at chemical equilibrium, a change in the system will cause the system to shift in the direction that will increase the change's effect and keep the reaction from regaining chemical equilibrium.

c. when a reaction is at chemical equilibrium, a change in the system will cause the system to become an irreversible reaction until it regains chemical equilibrium.

d. when a reaction is at chemical equilibrium, a change in the system will cause the system to become an irreversible reaction and become unable to regain chemical equilibrium.