Question: which gas is responsible for depletion of ozone layer around earth
[{'answer': 'halogen', 'provenance': [{'wikipedia_id': '44183', 'title': 'Ozone depletion', 'start_paragraph_id': 2, 'start_character': 470, 'end_paragraph_id': 2, 'end_character': 477, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '44183', 'title': 'Ozone depletion', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 663, 'bleu_score': 0.749477971551282, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11979519829210631535}, 'section': 'Section::::Abstract.'}]}]