Question: which molecule or ion needs only two resonance structures to describe its bonding
[{'answer': 'ozone molecule', 'provenance': [{'wikipedia_id': '271046', 'title': 'Resonance (chemistry)', 'start_paragraph_id': 34, 'start_character': 4, 'end_paragraph_id': 34, 'end_character': 18, 'bleu_score': 1.0, 'section': 'Section::::Examples.:Electron-rich molecules.\n'}]}, {'provenance': [{'wikipedia_id': '271046', 'title': 'Resonance (chemistry)', 'start_paragraph_id': 34, 'start_character': 0, 'end_paragraph_id': 34, 'end_character': 276, 'bleu_score': 0.8879659171421961, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17621136983603444014}, 'section': 'Section::::Examples.:Electron-rich molecules.\n'}]}]