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

Question

( A ) $H_2^{2+}, He_2$
( B ) $H_2^{-}, He_2^{2-}$
( C ) $H_2^{2+}, He_2^{2-}$
( D ) $H_2^{-}, He_2^{2+}$