Answer:
Option B
Explanation:
According to molecular orbital theory , species with all paired electrons in their electronic configuration are diamagnetic in nature
He^{+}_{2}\rightarrow Has total 3 electrons , thus it contains one unpaired electron and is paramagnetic in nature.
H_{2}\rightarrow Has total 2 electrons , thus it contains all paired electrons and is diamagnetic in nature
H^{-}_{2}\rightarrow Has only 1 electron, thus it is paramagnetic in nature
H^{2}_{2}\rightarrow Has total 3 electrons, thus it contains one unpaired electron and is paramagnetic in nature
He \rightarrow Contains total two (2) electrons and has no unpaired electron, thus is diamagnetic in nature.
Hence , among the given species, we have only two of them which are diamagnetic and thus, option (b) is the correct answer.