Which amongst the following is incorrect statement
A $O_2^+$ ion is diamagnetic.
B The bond orders of $O_2^+$, $O_2$, $O_2^-$ and $O_2^{2-}$ are 2.5, 2, 1.5 and 1, respectively
C $C_2$ molecule has four electrons in its two degenerate $\pi$ molecular orbitals.
D $H_2^+$ ion has one electron.