Which of the following is a characteristic property of equilibrium?

On addition of a catalyst, the value of ${\mathrm{K}}_{\mathrm{c}}$ does not change for a reaction in equilibrium because catalyst speeds up the rate of forward and backward reaction to the same extent.

Rate of forward reaction is equal to the rate of backward reaction at equilibrium.

After reaching the chemical equilibrium, the concentrations of reactants and products remain unchanged with time. After reaching the equilibrium, both forward and backward reaction continue to take place.