Which is a possible example of species that can comprise a buffer solution?

Question

CH3COOH and NaCH3COO

CH3OH and CH3COOH

HCl and NaOH

H2O and NaOH

Answer 1

CH3COOH and NaCH3COO^-

This is the only choice that has a weak acid (CH3COOH) and the salt of that acid NaCH3COO^-.

This is what is required to make a buffer.