The diagram below shows a diagrammatic sketch of the maturation of insulin. Select the correct set of names labeled $A, B, C$,and $D$.

• A
  $A-A$-peptide,$B-B$-peptide,$C$-Proinsulin,$D$-Free $C$-Peptide
• B
  $A$-Proinsulin,$B$-$A$ peptide,$C$-$B$ peptide,$D$-free $C$-Peptide
• C
  $A$-Free $C$-Peptide,$B$-$A$-peptide,$C$-$B$-peptide,$D$-Proinsulin
• D
  $A$-$A$-peptide,$B$-$B$-peptide,$C$-Free $C$-peptide,$D$-Proinsulin