Question: when did germany first use poison gas in ww1
[{'answer': '31 January 1915', 'provenance': [{'wikipedia_id': '167578', 'title': 'Chemical weapons in World War I', 'start_paragraph_id': 9, 'start_character': 64, 'end_paragraph_id': 9, 'end_character': 79, 'bleu_score': 1.0, 'section': 'Section::::History of poison gas in World War I.:1915: Large-scale use and lethal gases.\n'}]}, {'provenance': [{'wikipedia_id': '167578', 'title': 'Chemical weapons in World War I', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 330, 'bleu_score': 0.9224532597476071, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5156603891313324242}, 'section': 'Section::::History of poison gas in World War I.:1915: Large-scale use and lethal gases.\n'}]}]