Answer: b. an individual oxygen atom combines with an oxygen molecule
Explanation:
Molecules of an element is a pure substance which is composed of atoms of similar elements. Example: [tex]O_2[/tex]
Atom is the smallest entity of a matter which has its independent existence.
[tex]O_2+O\rightarrow O_3[/tex]
Ozone is a molecule of oxygen which contains 3 oxygen atoms and hence is formed by the combination of a molecule of oxygen and a atom of oxygen.
Hence the correct option is b.
