According to molecular orbital theory

• A

  ${\mathrm{C}}_2^{2-}\text{ is expected to be diamagnetic }$

• B

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

• C

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

• D

  ${\mathrm{He}}_2^{+}\text{has the same energy as two isolated }\mathrm{He}\text{ atoms. }$