Which one of the following is not a green house gas

• A

  ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

• B

  ${\mathrm{CH}}_4$

• C

  ${\mathrm{N}}_2$

• D

  ${\mathrm{CCl}}_2{\mathrm{F}}_2$