Answer this & explain im so confused

Question

I think the correct answer is the second one but not sure..

A solution is prepared by mixing equal volumes of 0.20M HC₂H₃O₂ and 0.40M NaC₂H₃O₂. Which of the following correctly describes what occurs if a small amount of HCl (aq) or NaOH (aq) is added?

1. If NaOH (aq) is added, the pH will increase only slightly because the OH⁻ ions will react with HC₂H₃O₂ molecules.
2. If HCl (aq) is added, the pH will decrease only slightly because the H⁺ ions will react with HC₂H₃O₂ molecules.
3. If HCl (aq) is added, the pH will increase only slightly because the Cl⁻ ions will react with C₂H₃O₂⁻ ions.
4. If NaOH (aq) is added, the pH will decrease only slightly because the OH⁻ ions will react with C₂H₃O₂⁻ ions.

Answer 1

If NaOH (aq) is added, the pH will increase only slightly because the OH⁻ ions will react with HC₂H₃O₂ molecules.

Explanation:

The mixture of HC₂H₃O₂ and C₂H₃O₂^- creates a buffer solution. If you add NaOH, or simply OH^-, it will react with the acid, HC₂H₃O₂ to produce H₂O and C₂H₃O₂^-. This is why the first answer is correct.

The 2nd answer is not correct, because if HCl is added the pH will decrease slightly because the H⁺ will react with the C₂H₃O₂^- to produce HC₂H₃O₂ (a weak acid). It won't react with HC₂H₃O₂ .