An Energy Level Scheme for the Orbitals of Second Row $\sigma$

An energy level scheme for the orbitals of second row diatomic molecules O₂ through Ne₂ , lists the molecular orbitals in the following order of increasing energy $\sigma$ _2s < $\sigma$ *_2s < $\sigma$ _2p(z) < $\pi$ _2p(y) , $\pi$ _2p(x) < $\pi$ *_2p(y) , $\pi$ *_2p(x) < $\sigma$ *_2p(z)
Based on this energy level scheme, how many unpaired electrons are in all of the antibonding molecular orbitals of the O₂^- ion in its ground state?

A) 1
B) 2
C) 3
D) 4
E) 5