The correct statement is:
D. O2 is a molecule while CO2 is a compound.
Explanation:
- O2 is a diatomic molecule consisting of two oxygen atoms. It is not considered a compound because it is made up of only one type of element (oxygen).
- CO2 is a compound made of one carbon atom and two oxygen atoms, consisting of different elements.
So, O2 qualifies as a molecule, while CO2 is a compound.