Question: when was the last time the emergency broadcast system was used
[{'answer': '1997', 'provenance': [{'wikipedia_id': '77687', 'title': 'Emergency Broadcast System', 'start_paragraph_id': 1, 'start_character': 267, 'end_paragraph_id': 1, 'end_character': 271, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '77687', 'title': 'Emergency Broadcast System', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 333, 'bleu_score': 0.7707148210225361, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8673112406968528563}, 'section': 'Section::::Abstract.'}]}]