$NH_3 + O_2 \xrightarrow[\Delta ]{Pt} A + H_2O;$ $A + O_2 \to B;$ $B + O_2 + H_2O \to C$
$A, B$ and $C$ are

• A
  $N_2O, NO_2$ and $HNO_3$
• B
  $NO, NO_2$ and $HNO_3$
• C
  $NO_2, NO$ and $HNO_3$
• D
  $N_2O, NO$ and $HNO_3$