The heating of $NH _4 NO _2$ at $60-70^{\circ} C$ and $NH _4 NO _3$ at $200-250^{\circ} C$ is associated with the formation of nitrogen containing compounds $X$ and $Y$, respectively. $X$ and $Y$, respectively, are

• A
  $N _2$ and $N _2 O$
• B
  $NH _3$ and $NO _2$
• C
  $NO$ and $N _2 O$
• D
  $N _2$ and $NH _3$