Execution of Strategy: (a) HF and NaF are mixed. HF and F- will both be present. This will make a buffer.

What happens in a buffer system of HF and NaF?

In a buffer system of HF and its salt, NaF, the HF neutralizes added base.

What forms a buffer with HF?

(D) HF and NaOH

(D) This will form a buffer if you have half as much NaOH as HF. When you neutralize HF with NaOH, you form F-, the conjugate base of HF.