Given below is the sequence of events in the production of human insulin by Eli Lilly.
$(a)$ Preparation of two $DNA$ sequences corresponding to chain $A$ and $B$ of human insulin.
$(b)$ Production of chain $A$ and $B$ separately.
$(c)$ Introduction of chains in plasmids of $E. coli$.
$(d)$ Extraction of chain $A$ and $B$ and combining them by creating disulphide bonds.
Choose the correct sequence of events.

• A
  $(a)$, $(b)$, $(c)$, $(d)$
• B
  $(a)$, $(c)$, $(b)$, $(d)$
• C
  $(a)$, $(b)$, $(d)$, $(c)$
• D
  $(a)$, $(d)$, $(b)$, $(c)$