Answer: B. CO
Explanation:
Diatomic molecules are those that are formed by two atoms of the same chemical element (homonuclear diatomic molecule) or different chemical element (heteronuclear diatomic molecule).
In this sense, oxygen is a homonuclear diatomic molecule because it is formed by two atoms of the same element ([tex]O_{2}[/tex]) and Carbon monoxide ([tex]CO[/tex]) is heteronuclear diatomic molecule.
Sodium Chloride [tex]NaCl[/tex] is not a diatomic molecule because is a product of ionization, but it can be diatomic in its gas phase with a polar covalent bond.
