Explanation

(c)
A species is said to be diamagnetic if it has all electrons paired
[table] Species | Electrons | MO electronic configuration | Magnetic behaviour ; $H_{2}^{-}$
$H_{2}^{+}$
$H_{2}$
${He}_{2}^{+}$ | 3
1
2
3 | $\sigma 1s^{2}\ _{\sigma}^{*}1s^{1}$
$\sigma 1s^{1}$
$\sigma 1s^{2}$
$\sigma 1s^{2}\ _{\sigma}^{*}1s^{1}$ | Paramagnetic
Paramagnetic
Diamagnetic
Paramagnetic [/table]