The correct option is
C Val → Leu(1) DBP method or Leucine aminopeptidase enzyme releases N-terminal amino acid.Tetrapeptide(I)⟶Alanine(N−terminal)+TripeptideAla(N−terminal)⟶Tripeptide(2) Hydrazinolys or carboxypeptidase enzyme releases C-terminal amino acid.Tetrapeptide(I)⟶Dipeptide+Glycine(C−terminal)Ala(N−terminal)⟶Dipeptide⟶Gly(C−terminal)(3) Dipeptide (III) now contains only two amino acids, valine and Leucine. Edman method releases N-terminal amino acid.Dipeptide(III)⟶Valine(N−terminal)⟶Leucine(C−terminal)Hence, option A is correct.