Diagram 9-1 the Molecular Orbital Diagram Below May Be Used $\sigma$

Multiple Choice

Diagram 9-1 The molecular orbital diagram below may be used for the following problem(s) .For oxygen and fluorine,the $\sigma$ _2p orbital should be lower in energy than the $\pi$ _2p orbitals.However,the diagram will still yield correct bond order and magnetic behavior for these molecules.
-Refer to Diagram 9-1.According to molecular orbital theory,which of the following species will have only $\underline{\text{ one }}$ unpaired electron?

A) B₂
B) O₂^2-
C) C₂
D) O₂
E) N₂⁺