Which of the following species exhibits diamagnetic behaviour?

A species is diamagnetic if all its electrons are paired.${\text{O}}_2$ (16e): Paramagnetic (2 unpaired electrons in ${\pi }^{\ast }$ orbitals).${\text{O}}_2^{+}$ (15e): Paramagnetic (1 unpaired electron).$\text{NO}$ (15e): Paramagnetic (1 unpaired electron).${\text{O}}_2^{2-}$ (18e): Peroxide ion.Configuration: $\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2\pi 2p_x^2\pi 2p_y^2{\pi }^{\ast }2p_x^2{\pi }^{\ast }2p_y^2$.All electrons are paired. Thus, it is diamagnetic.