Question: what's the tallest building in the world right now
[{'answer': 'Burj Khalifa', 'provenance': [{'wikipedia_id': '338344', 'title': 'List of tallest buildings', 'start_paragraph_id': 2, 'start_character': 671, 'end_paragraph_id': 2, 'end_character': 683, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]