Which of the following is a zero order reaction?

• A

  $2 \mathrm{HI} \rightarrow \mathrm{H}_2+\mathrm{I}_2$
• B

  $\mathrm{H}_2+\mathrm{Br}_2 \underset{\Delta}{\longrightarrow} 2 \mathrm{HBr}$
• C

  $2 \mathrm{~N}_2 \mathrm{O}_5 \rightarrow 4 \mathrm{NO}_2+\mathrm{O}_2$
• Correct answer
  D

  $\mathrm{H}_2+\mathrm{Cl}_2 \stackrel{\text { hv }}{\longrightarrow} 2 \mathrm{HCl}$

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