Question: what is the new tallest building in san francisco
[{'answer': 'Salesforce Tower', 'provenance': [{'wikipedia_id': '38943481', 'title': 'Salesforce Tower', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 16, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]