Question: who was the secretary general of the united nations
[{'answer': 'Gladwyn Jebb'}, {'answer': 'Trygve Lie'}, {'answer': 'Dag Hammarskjöld'}, {'answer': 'U Thant'}, {'answer': 'Kurt Waldheim', 'provenance': [{'wikipedia_id': '162415', 'title': 'Secretary-General of the United Nations', 'start_paragraph_id': 11, 'start_character': 395, 'end_paragraph_id': 11, 'end_character': 408, 'bleu_score': 1.0, 'section': 'Section::::Selection and term of office.\n'}]}, {'answer': 'Javier Pérez de Cuéllar', 'provenance': [{'wikipedia_id': '162415', 'title': 'Secretary-General of the United Nations', 'start_paragraph_id': 19, 'start_character': 67, 'end_paragraph_id': 19, 'end_character': 90, 'bleu_score': 1.0, 'section': 'Section::::Living former Secretaries-General.\n'}]}, {'answer': 'Boutros Boutros - Ghali', 'provenance': [{'wikipedia_id': '162415', 'title': 'Secretary-General of the United Nations', 'start_paragraph_id': 11, 'start_character': 217, 'end_paragraph_id': 11, 'end_character': 239, 'bleu_score': 1.0, 'section': 'Section::::Selection and term of office.\n'}]}, {'answer': 'Kofi Annan', 'provenance': [{'wikipedia_id': '162415', 'title': 'Secretary-General of the United Nations', 'start_paragraph_id': 19, 'start_character': 172, 'end_paragraph_id': 19, 'end_character': 182, 'bleu_score': 1.0, 'section': 'Section::::Living former Secretaries-General.\n'}]}, {'answer': 'Ban Ki - moon'}]