How many species of the following would involve HP mixing?

${\mathrm{B}}_2,{\mathrm{O}}_2,{\mathrm{F}}_2,{\mathrm{N}}_2,{\mathrm{O}}_2^{+},{\mathrm{F}}_2^{-},{\mathrm{C}}_2,{\mathrm{O}}_2^{-}$

The SP mixing occurs when molecular orbitals of the same symmetry formed  $2\mathrm{S}- 2\mathrm{P}$.

So, $B_2,N_2,C_2$ are the molecule which is diamagnetic.