You Want to Maintain PH = 7

You want to maintain pH = 7.0 for an enzyme-catalyzed reaction that will produce hydrogen ions along with the desired product.At equal concentrations,which weak acid,if any,will serve as the better buffer for the reaction: Acid A,with pKa = 6.5 or Acid B,with pKa = 7.5?

A) Acid A
B) Water is as good as either of the acids available.
C) Acid B
D) Both are equally effective.