In a buffter system of [tex]\mathrm{HF}[/tex] and its salt, [tex]\mathrm{NaF}[/tex].
the [tex]\mathrm{F}[/tex] neutralizes added [tex]\mathrm{H}_2 \mathrm{O}[/tex].
the HF is not necessary
the HF neutralizes added acid
the HF neutralizes added base
the F' neutralizes added base