Answer: Option (c) is the correct answer.
Explanation:
A molecule is defined as a substance which can contain atoms of same or different elements that are chemically combined together.
For example, [tex]Cl_{2}[/tex], [tex]O_{2}[/tex], [tex]MgCl_{2}[/tex] etc are molecules.
Whereas a compound is defined as a chemical specie which is made by the combination of different atoms in a fixed ratio by mass.
For Example, [tex]H_2O[/tex], [tex]CO_2[/tex] etc. are compounds.
A compound will also be considered as a molecule but a molecule can never be considered as a compound.
And, a molecule of an element will always contain atoms of one type of element.
As in the given situation both W and Z atoms represent the same element, that is, oxygen.
Thus, we can conclude that W and Z atoms could join together to form a molecule of an element.
