Question: when was the first us aircraft carrier built
[{'answer': '1920', 'provenance': [{'wikipedia_id': '199421', 'title': 'USS Langley (CV-1)', 'start_paragraph_id': 1, 'start_character': 92, 'end_paragraph_id': 1, 'end_character': 96, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '199421', 'title': 'USS Langley (CV-1)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 784, 'bleu_score': 0.854035470989671, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6391882909173860072}, 'section': 'Section::::Abstract.'}]}]