Final answer:
The best Lewis structure with a resonance structure from the given options is NO₂⁻ (nitrite ion), as it has two resonance forms due to the possibility of moving the double bond between the two oxygen atoms.
Step-by-step explanation:
The best Lewis structure that includes a resonance structure among the given options is NO₂⁻ (nitrite ion). Resonance structures are used when a single Lewis structure is inadequate to represent a molecule or ion. In the case of NO₂⁻, there are two equally valid structures that differ only in the placement of the double bond, and they contribute to the overall structure of the ion.
For CO₂ (carbon dioxide), it has a single, stable Lewis structure without resonance as the carbon atom forms double bonds with each oxygen atom. In the case of SO₃ (sulfur trioxide), similarly, there are three resonance structures as the double bonds can be placed between sulfur and any of the three oxygen atoms. And finally, for CH₄ (methane), it has no resonance structures as it contains four single bonds between carbon and hydrogen.