Which one of the following mixture acts like an acidic buffer

1  .  .  .HCl10  meq+NH4OH10  meq;It is a salt of strong acid and weak base….not a buffer;2  .  .  . CH3COOH10  meq+NaOH5  meqExcess weak acid and limited strong base…. mixture acts like acidic buffer(3)…salt of strong acid and strong base….not a buffer;(4)…..mixture of strong base and a salt….not a buffer;