Question: when did northern rhodesia became a british protectorate
[{'answer': '1911', 'provenance': [{'wikipedia_id': '284309', 'title': 'Northern Rhodesia', 'start_paragraph_id': 1, 'start_character': 72, 'end_paragraph_id': 1, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '284309', 'title': 'Northern Rhodesia', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 591, 'bleu_score': 0.9768747032089851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16028965930825743839}, 'section': 'Section::::Abstract.'}]}]