O₂,also Termed Atmospheric Oxygen,is Considered to Be a Molecule but Not

O₂,also termed atmospheric oxygen,is considered to be a molecule but not a compound;why not?

A) It contains no covalent bonds.
B) It contains a double covalent bond but not a single covalent bond.
C) To be considered a compound,there must be a minimum of three atoms;atmospheric oxygen is too small.
D) Compounds are defined as molecules constructed from two or more different elements.