Question: when did britain become the most powerful empire
[{'answer': '1913', 'provenance': [{'wikipedia_id': '4721', 'title': 'British Empire', 'start_paragraph_id': 1, 'start_character': 416, 'end_paragraph_id': 1, 'end_character': 420, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4721', 'title': 'British Empire', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 886, 'bleu_score': 0.911448926473517, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16059876648013512680}, 'section': 'Section::::Abstract.'}]}]