You Need to Prepare a Buffer Solution with a PH

Multiple Choice

You need to prepare a buffer solution with a pH of 4.00, using NaF and HF. What ratio of the ratio of [base]/[acid] should be used in making the buffer? For HF, K_a = 7.2 * 10¯⁴

A) [base]/[acid] = 0.14
B) [base]/[acid] = 0.42
C) [base]/[acid] = 2.36
D) [base]/[acid] = 7.20
E) None of these choices is correct.