Question: when did the aria hotel in las vegas open
[{'answer': 'December 16 , 2009', 'provenance': [{'wikipedia_id': '22724379', 'title': 'Aria Resort and Casino', 'start_paragraph_id': 7, 'start_character': 587, 'end_paragraph_id': 7, 'end_character': 605, 'bleu_score': 1.0, 'section': 'Section::::History.:Construction, opening.\n'}]}]