Suppose you are asked to prepare a buffer solution of pH 6.5 which is having the buffer capacity of 0.1 using NaH2PO4 (acid) and Na2HPO4 (salt). Which of following combination of the buffer species can be used to make such a buffer? Where the pKa for NaH2PO4 (acid) ionizes to Na2HPO4+H+ is 7.21