Which of the following is an example of a first-order reaction?

• A
  $CH_3CHO_{(g)} \rightarrow CH_{4_{(g)}} + CO_{(g)}$
• B
  $2NO_{2_{(g)}} + F_{2_{(g)}} \rightarrow 2NO_2F_{(g)}$
• C
  $2NO_{(g)} + 2H_{2_{(g)}} \rightarrow N_{2_{(g)}} + 2H_2O_{(g)}$
• D
  $2H_2O_{2_{(aq)}} \rightarrow 2H_2O_{(l)} + O_{2_{(g)}}$