Which of the following conversions need the reagent $\mathrm{Sn} / \mathrm{HCl}$ ?

• A

  $\mathrm{R}-\mathrm{CO}-\mathrm{NH}_2 \rightarrow \mathrm{R}-\mathrm{CH}_2-\mathrm{NH}_2$
• B

  $\mathrm{R}-\mathrm{C} \equiv \mathrm{N} \rightarrow \mathrm{R}-\mathrm{CH}_2-\mathrm{NH}_2$
• Correct answer
  C

  $\mathrm{R}-\mathrm{NO}_2 \rightarrow \mathrm{R}-\mathrm{NH}_2+2 \mathrm{H}_2 \mathrm{O}$
• D

  $\mathrm{R}-\mathrm{CO}-\mathrm{HN}_2 \rightarrow \mathrm{R}-\mathrm{NH}_2$

Hence, the correct answer is option: 'C'.