Which diagram(s) best represent(s) only diatomic molecules?

To determine which diagram represents only diatomic molecules, it is important to first understand what diatomic molecules are. Diatomic molecules consist of two atoms, which can be of the same element (like O2 or N2) or of different elements (like CO or HCl).

When examining the diagrams, you would look for indications that each illustrated molecule contains precisely two atoms. If one of the diagrams depicts molecules that contain more than two atoms or incorrect atom combinations, it cannot solely represent diatomic molecules.

Choosing the option that correctly identifies only those diagrams that show pairs of atoms verifies that only diatomic molecules are being represented. By confirming that the selected diagram contains representations of diatomic molecules exclusively, it would clarify that the answer is correct. Hence, the conclusion that only one specific diagram accurately depicts diatomic molecules leads to the final answer given.

In this instance, if only the second diagram shows pairs of atoms without additional atoms or complexes, it solidifies why it is the correct selection. The presence of singular diatomic pairs in that diagram affirms the choice made.