You have to prepare a pH = 3.50 buffer, and you have the following 0.10 M solutions available: HCOOH, CH₃COOH, H₃PO₄, HCOONa, CH₃COONa, and NaH₂PO₄. Which solutions would you use?
a) HCOOH and CH₃COONa
b) CH₃COOH and NaH₂PO₄
c) H₃PO₄ and HCOONa
d) CH₃COOH and HCOONa