1 answer
(click or scroll down)
The correct choice that only includes terms that describe oxygen gas (O2) is: **atom, compound, molecule**.
However, please note that the best answer from a conceptual standpoint would actually be **molecule, pure substance**, but that is not one of the options provided. The term "element" generally applies to the individual types of atoms, not the gas itself, which is molecular (O2 is a diatomic molecule). Therefore, "compound" would not be appropriate either since O2 is not a compound but an elemental gas.
Given your options, the closest terms describing oxygen gas specifically would still fit in the category of being a **molecule and a pure substance**.