What mixture makes up a buffer solution?

1. A buffer holds a weak acid and its conjugate base together in the same solution. 2. A weak base with its conjugate acid works equally well and is the other standard form. 3. Acetic acid with sodium acetate is the classic weak acid version. 4. Ammonia with ammonium chloride is the classic weak base version. 5. Two strong species would simply neutralise each other and buffer nothing. _Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.6 Buffers_