Which amongst the following is an incorrect statement?

• A
  $C_{2}$ molecule has four electrons in its two degenerate $\pi$ molecular orbitals.
• B
  $H_{2}^{+}$ ion has one electron.
• C
  $O_{2}^{+}$ ion is diamagnetic.
• D
  The bond orders of $O_{2}^{+}, O_{2}, O_{2}^{-}$ and $O_{2}^{2-}$ are $2.5, 2, 1.5$ and $1,$ respectively.