This is an easy one: none.
The oxygen atom, or molecule (unspecified) "contain" parts which are given some sort of indipendent existence, which are the following: nucleus (or nuclei) with their subcomponents, internal and peripheral electrons.
Orbitals are not real objects that might be somewhat contained or be part of any real object. They are a mathematical model reproducing some properties of the atom's energy and of symmetry of the electron cloud.
So, a more interesting question could be: "how many hydrogenlike orbitals are necessary to describe the energy distribution of the electrons in an oxygen atom?", or "how many molecular orbitals are needed to describe the energetic and magnetic behavior of an oxygen molecule within the Molecular Orbital theory?"