Which amongst the following is incorrect statement?

$\displaystyle \mathrm{O}_2^{+}$ion is diamagnetic.

The bond orders of $\displaystyle \mathrm{O}_2^{+}, \mathrm{O}_2, \mathrm{O}_2^{-}$and $\displaystyle \mathrm{O}_2^{2-}$ are $\displaystyle 2.5$, $\displaystyle 2$, $\displaystyle 1.5$ and $\displaystyle 1$, respectively.

$\displaystyle \mathrm{C}_2$ molecule has four electrons in its two degenerate $\displaystyle \pi$ molecular orbitals.

$\displaystyle \mathrm{H}_2^{+}$ion has one electron.