Question: the centers of most cities became business areas after the invention of what
[{'answer': 'skyscraper', 'provenance': [{'wikipedia_id': '251024', 'title': 'Downtown', 'start_paragraph_id': 7, 'start_character': 489, 'end_paragraph_id': 7, 'end_character': 499, 'bleu_score': 1.0, 'section': 'Section::::History.:Origins.\n'}]}, {'provenance': [{'wikipedia_id': '251024', 'title': 'Downtown', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 964, 'bleu_score': 0.987987443031558, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1058188104134929225}, 'section': 'Section::::History.:Skyscrapers.\n'}]}]