Question: when was the union of south africa formed
[{'answer': '31 May 1910', 'provenance': [{'wikipedia_id': '44555', 'title': 'Union of South Africa', 'start_paragraph_id': 1, 'start_character': 128, 'end_paragraph_id': 1, 'end_character': 139, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]