Question: which is the tallest building in the world 2018
[{'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.'}]}, {'answer': 'Burj Khalifa in Dubai', 'provenance': [{'wikipedia_id': '338344', 'title': 'List of tallest buildings', 'start_paragraph_id': 5, 'start_character': 333, 'end_paragraph_id': 5, 'end_character': 354, 'bleu_score': 1.0, 'section': 'Section::::Ranking criteria and alternatives.\n'}]}, {'provenance': [{'wikipedia_id': '338344', 'title': 'List of tallest buildings', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11671909573791766080}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '338344', 'title': 'List of tallest buildings', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 539, 'bleu_score': 0.891707079638387, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11671909573791766080}, 'section': 'Section::::Ranking criteria and alternatives.\n'}]}, {'provenance': [{'wikipedia_id': '3970948', 'title': 'Contemporary architecture', 'section': 'Section::::Skyscrapers.\n', 'start_paragraph_id': 26, 'end_paragraph_id': 26, 'meta': {'evidence_span': ['The Burj Khalifa in Dubai, United Arab Emirates is the tallest structure in the world,', 'buildings, which needed fewer interior walls, had more window space, and could better resist lateral forces, such as strong winds. The Burj Khalifa in Dubai, United Arab Emirates is the tallest structure in the world, standing at . Construction of the Burj Khalifa began in 2004, with the exterior completed 5 years later in 2009. The primary structure is reinforced concrete. Burj Khalifa was designed by Adrian Smith, then of Skidmore, Owings & Merrill (SOM). He also was lead architect on the Jin Mao Tower, Pearl River Tower, and Trump International Hotel & Tower\rhighlight sentence(s) containing evidence, not only the answer', 'Burj Khalifa in Dubai, United Arab Emirates is the tallest structure in the world, standing at .']}}]}, {'provenance': [{'wikipedia_id': '42293544', 'title': 'List of future tallest buildings', 'section': 'Section::::Future tallest.\n', 'start_paragraph_id': 3, 'end_paragraph_id': 3, 'meta': {'evidence_span': ["The Burj Khalifa with a roof height of is currently the world's tallest building.", "The Burj Khalifa with a roof height of is currently the world's tallest building."]}}]}, {'provenance': [{'wikipedia_id': '42293544', 'title': 'List of future tallest buildings', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ["The Burj Khalifa with a roof height of is currently the world's tallest building.", "This list of future tallest buildings ranks the tallest buildings in the world which are planned or currently under construction. The Burj Khalifa with a roof height of is currently the world's tallest building.", "The Burj Khalifa with a roof height of is currently the world's tallest building."]}}]}]