Which of the following is paramagnetic?

Key Idea If all the electron in a molecule are paired, the molecule is diamagnetic and if there are unpaired electrons in a molecule, it is paramagnetic. Molecular orbital configuration of given molecules are as follows: (1) $\mathrm{N}_2(\mathrm{Z}=14)-\sigma \mathrm{ls}^2, \sigma^* 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \sigma{ }^* 2 \mathrm{~s}^2, \pi 2 \mathrm{p}_{\mathrm{x}}^2=\pi 2 \mathrm{p}_{\mathrm{y}}^2, \sigma 2 \mathrm{p}_{\mathrm{z}}^2$ It is a diamagnetic molecule due to absence of unpaired electron. (2) $\mathrm{H}_2(\mathrm{Z}=2)-1 \sigma^2$ It is a diamagnetic molecule. (3) $\mathrm{Li}_2(\mathrm{Z}=6)-\sigma \mathrm{ls}^2, \sigma{ }^* 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2$ It is a diamagnetic molecule. (4) $\mathrm{O}_2(\mathrm{Z}=16)-\sigma \mathrm{ls}^2, \sigma{ }^* 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \sigma * 2 \mathrm{~s}^2$, $\sigma$2 p_z^2, $\pi$2 p_x^2=$\pi$2 p_y^2, $\pi$* 2 p_x^1=$\pi$* 2 p_y^1 It is a paramagnetic molecule due to presence of unpaired electrons in each orbital of degenerate levels. Thus, option (4) is correct.