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.Assume that the molecular orbital energy diagram for a homonuclear diatomic molecule applies to a heteronuclear diatomic molecule.What is the molecular orbital configuration of CO?

A) [core electrons] ( $\sigma$ _2s) ² ( $\sigma$ *_2s) ² ( $\pi$ _2p) ⁴ ( $\sigma$ _2p) ²
B) [core electrons] ( $\sigma$ _2s) ² ( $\sigma$ *_2s) ² ( $\pi$ _2p) ² ( $\sigma$ _2p) ² ( $\pi$ *_2p) ²
C) [core electrons] ( $\sigma$ _2s) ² ( $\sigma$ *_2s) ² ( $\pi$ _2p) ² ( $\sigma$ _2p) ⁴
D) [core electrons] ( $\sigma$ _2s) ² ( $\sigma$ *_2s) ² ( $\pi$ _2p) ⁶
E) [core electrons] ( $\sigma$ _2s) ² ( $\sigma$ *_2s) ² ( $\pi$ _2p) ³ ( $\sigma$ _2p) ³