Which of the following molecules is paramagnetic?

Among $H_2, He_2^{+}, Li_2, Be_2, B_2, C_2, N_2, O_2^{-}$,and $F_2$,the number of diamagnetic species is (Atomic numbers: $H=1, He=2, Li=3, Be=4, B=5, C=6, N=7, O=8, F=9$)

Correct order of $C-O$ bond length is:

The bond length of the species $O_2$,$O_2^+$ and $O_2^-$ are in the order of

Four diatomic species are listed below. Identify the correct order in which the bond order is increasing in them.

According to the molecular orbital theory,the bond order in $C_2$ molecule is