D i.e. C - PeptideInsulin has two interchain (A7 - B7, & A20 - B19) and one intrachain (A6 - All) disulfide bridges with in AB hetrodimeric structureQ.Insulin is synthesized as pre-pro-hormone (MW 11, 500), which makes it difficult to synthesize insulin in laboratory even after synthesizing A, B chains. This pre prohormone is directed by hydrophobic 23 aminoacid pre or leader sequence into cisternae of endoplasmic retinaculum, which is then removed to form 9000 MW proinsulin.Staing from amino terminal, the chain sequenc of proinsulin is.