An Acid-Base Equilibrium System Is Created by Dissolving 0

An acid-base equilibrium system is created by dissolving 0.50 mol CH₃CO₂H in water to a volume of 1.0 L.What is the effect of adding 0.50 mol CH₃CO₂^-(aq) to this solution?
1) The pH of the solution will equal 7.00 because equal concentrations of a weak acid and its conjugate base are present.
2) Some CH₃CO₂H(aq) will ionize,increasing the concentration of CH₃CO₂^-(aq) and increasing the pH.
3) Some CH₃CO₂^-(aq) will react with H₃O⁺,increasing the concentration of CH₃CO₂H(aq) and reestablishing the solution equilibrium.

A) 1 only
B) 2 only
C) 3 only
D) 1 and 3
E) 1,2,and 3