Which of the following species is diamagnetic in nature?

The molecular configurations are 

$\begin{array}{l}{\mathrm{H}}_2^{+}:(\sigma 1\mathrm{s}{)}^1\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{He}}_2^{+}:(\sigma 1\mathrm{s}{)}^2{\left({\sigma }^{\ast }1\mathrm{s}\right)}^1\\ {\mathrm{H}}_2^{-}:(\sigma 1\mathrm{s}{)}^2{\left({\sigma }^{\ast }1\mathrm{s}\right)}^1\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{H}}_2:(\sigma 1\mathrm{s}{)}^2\end{array}$

A diamagnetic substance does not possess unpaired electron. Dihydrogen does not possess unpaired electron; hence it is diamagnetic.