Which of the following species is diamagnetic?

$\mathrm{O}{}_2{}^{2-}$ has 14 valence electrons, with ${\pi }^{\ast }2p_x$ and ${\pi }^{\ast }2p_y$ both full, so all electrons are paired. $\mathrm{O}{}_2{}^{-}$, $\mathrm{O}{}_2{}^{+}$ and $\mathrm{NO}$ each have an odd number of electrons and are paramagnetic.