Which one of the following pairs of species have the same bond order?

• A

  ${\mathrm{O}}_2,{\mathrm{NO}}^{+}$

• B

  ${\mathrm{CN}}^{-},\mathrm{CO}$

• C

  ${\mathrm{N}}_2,{\mathrm{O}}_2^{-}$

• D

  $\mathrm{CO},\mathrm{NO}$