Respuesta :
Answer is: B) O2 is a molecule.
Pure substance is made of only one type of atom (element) or only one type of molecule (compound).
For example, hydrogen peroxide (H₂O₂), sodium chloride (NaCl) are compounds, lithium (Li) is an element and oxygen (O₂) is a molecule.
Molecules can be homonuclear (molecule made of two atoms of the same element, in this example oxygen) and heteronuclear (molecule made of two different atoms, for example water).