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

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 be diamagnetic?

A) He₂⁺
B) F₂^-
C) Li₂⁺
D) F₂
E) C₂⁺