Propose the reagents required for the following conversion.
butan-1-ol → 2-hydroxypentanoic acid

• A. i) PCC
  ii) NaOH
  iii) H₃O⁺ + heat
• B. i) PBr₃
  ii) Mg in ether
  iii) acetaldehyde
• C. i) PCC
  ii) KCN in HCN
• D. i) PCC
  ii) KCN in HCN
  iii) H₃O⁺ + heat

Answer: (D)