Question: when did south africa gained independence from britain
[{'answer': '31 May 1961', 'provenance': [{'wikipedia_id': '65638', 'title': 'History of South Africa', 'start_paragraph_id': 3, 'start_character': 535, 'end_paragraph_id': 3, 'end_character': 546, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '65638', 'title': 'History of South Africa', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 679, 'bleu_score': 0.7501873622621781, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7025171003377331085}, 'section': 'Section::::Abstract.'}]}]