In the reaction sequence $CH_3CH_2Br$ $\xrightarrow{AgCN} A$ $\xrightarrow{H_3O^+} HCOOH + B; B$ $\xrightarrow{CHCl_3/KOH} A$ $\xrightarrow{Reduction} C$,what are $A, B,$ and $C$ respectively?

• A
  Ethyl isocyanide,Ethylamine,and $N$-methylethanamine
• B
  Ethyl isocyanide,Ethylamine,and $N$-ethylethanamine
• C
  Ethyl cyanide,Ethylamine,and $N$-methylethanamine
• D
  Ethyl isocyanide,Methylamine,and $N$-methylethanamine