Which of the following is paramagnetic?

Which of the following species have the same bond order: $H_2^+$,$He_2^-$,and $He_2^{2-}$?

Which of the following statements is correct?

For diatomic molecules,the correct statement$(s)$ about the molecular orbitals formed by the overlap of two $2p_z$ orbitals is(are):
$(A)$ $\sigma$ orbital has a total of two nodal planes.
$(B)$ $\sigma^*$ orbital has one node in the $xz$-plane containing the molecular axis.
$(C)$ $\pi$ orbital has one node in the plane which is perpendicular to the molecular axis and goes through the center of the molecule.
$(D)$ $\pi^*$ orbital has one node in the $xy$-plane containing the molecular axis.

Which of the following is diamagnetic?

The incorrect statement regarding molecular orbital $(s)$ is