In CO there are a complete of fourteen electrons, a half dozen from C and 8 from O. The oxygen orbitals are reduce in energy because of their bigger nuclear charge. We may well construct the MOs in two alternatives, a) without taking into account the hybridization of the AOs of each and every atom as well as b) considering the hybridization of the AOs in every atom. The energy level diagram for the two the cases are shown in fig 1