Question: when did the construction of the burj khalifa end
[{'answer': '2010', 'provenance': [{'wikipedia_id': '794957', 'title': 'Burj Khalifa', 'start_paragraph_id': 1, 'start_character': 115, 'end_paragraph_id': 1, 'end_character': 119, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '794957', 'title': 'Burj Khalifa', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 819, 'bleu_score': 0.967405819735595, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4639535346403364947}, 'section': 'Section::::Abstract.'}]}]