A buffer that is most effective at a pH of about 4.5

MCQs AIIMS
#1
  1. A buffer that is most effective at a pH of about 4.5 is
    a) Acetate buffer
    b) Bicarbonate buffer
    c) Phosphate buffer
    d) Tris buffer

Explanation:
The solution resists changes in pH most effectively at pH values close to the pKa.
A solution of a weak acid and its conjugate base, buffers most effectively in the pH range pKa ± 1.0 pH unit.
Acid and pK:
Acetic: pK = 4.76
Carbonic: pK1=6.37 and pK2=10.25
Phosphoric: pK1= 2.15, pK2=6.82 and pK3=12.38
Answer: Acetate buffer
Ref: Harper 30th Ed. Page-