The correct option is B To bring A and B chain in correct orientation to form active insulin
Proinsulin when produced naturally, has an N terminal signal peptide, A and B chain, and a C peptide. The C peptide is required for forming correct three dimensional structure of active insulin by bringing A and B chains in correct orientation. In the formation of mature insulin, the C peptide is edited out after disulphide linkages are formed between the A and B chains.