Which molecule has the highest bond order

In which $O-O$ bond distance is minimum

Among the following molecules / ions $C_2^{2-} ,N_2^{2-} ,O_2^{2-},O_2$ which one is diamagnetic and has the shortest bond length ?

Explain formation of $\mathrm{H}_{2}$ and energy level diagram of $\mathrm{H}_{2}$ molecule.

According to Molecular Orbital Theory,

($A$) $\mathrm{C}_2^{2-}$ is expected to be diamagnetic

($B$) $\mathrm{O}_2{ }^{2+}$ is expected to have a longer bond length than $\mathrm{O}_2$

($C$) $\mathrm{N}_2^{+}$and $\mathrm{N}_2^{-}$have the same bond order

($D$) $\mathrm{He}_2^{+}$has the same energy as two isolated He atoms

The molecule in which hybrid $MOs$ involve only one $d-$orbital of the central atom is