In which of the following pairs of molecules/ions, both the species are not likely to exist?

A species is not likely to exist if its Bond Order (B.O.) is zero.${\text{H}}_2^{2+}$: Hydrogen has 2 electrons; ${\text{H}}_2^{2+}$ has 0 electrons. $\text{B.O.}=0$.${\text{He}}_2$: Helium has 2 electrons; ${\text{He}}_2$ has 4 electrons ($\sigma 1s^2,{\sigma }^{\ast }1s^2$). $\text{B.O.}=\frac{2-2}{2}=0$.Since both have B.O. 0, they are not likely to exist.