Which solution can be added to HCOOH(aq)\text{HCOOH(aq)}HCOOH(aq) to make a buffer solution?
HCOONa(aq)\text{HCOONa(aq)}HCOONa(aq)
HCl(aq)\text{HCl(aq)}HCl(aq)
NaCl(aq)\text{NaCl(aq)}NaCl(aq)
CH3COOH(aq)\text{CH}_3\text{COOH(aq)}CH3COOH(aq)