Which of the following molecules/ions does not contain unpaired electrons?

We use Molecular Orbital (MO) Theory:${\text{O}}_2$: Paramagnetic with $2$ unpaired electrons in ${\pi }^{\ast }2p_x$ and ${\pi }^{\ast }2p_y$.${\text{B}}_2$: Paramagnetic with $2$ unpaired electrons in $\pi 2p_x$ and $\pi 2p_y$.${\text{N}}_2^{+}$: Total electrons $13$. Configuration $\dots (\pi 2p_x{)}^2(\pi 2p_y{)}^2(\sigma 2p_z{)}^1$. Has $1$ unpaired electron.${\text{O}}_2^{2-}$: Total electrons $18$. Configuration $\dots (\pi 2p_x{)}^2(\pi 2p_y{)}^2(\sigma 2p_z{)}^2({\pi }^{\ast }2p_x{)}^2({\pi }^{\ast }2p_y{)}^2$. All electrons are paired.