Question: who become the first president of south africa in 1994
[{'answer': 'Nelson Rolihlahla Mandela', 'provenance': [{'wikipedia_id': '21492751', 'title': 'Nelson Mandela', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 25, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '21492751', 'title': 'Nelson Mandela', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 598, 'bleu_score': 0.921097057494161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8469955045210152863}, 'section': 'Section::::Abstract.'}]}]