A student prepares a buffer solution by combining \(50.0\text{ mL}\) of \(0.20\text{ M }\text{HC}_3\text{H}_5\text{O}_2\text{(aq)}\) and \(50.0\text{ mL}\) of \(0.20\text{ M }\text{NaC}_3\text{H}_5\text{O}_2\text{(aq)}\). To this buffer, a few drops of \(6.0\text{ M }\text{HCl(aq)}\) are added, resulting in only a negligible decrease in \(\text{pH}\). Which of the following is the net ionic equation that best represents the primary reaction responsible for resisting the \(\text{pH}\) change upon addition of the acid?