Question: when was the san francisco international airport built
[{'answer': '1931', 'provenance': [{'wikipedia_id': '250462', 'title': 'San Francisco International Airport', 'start_paragraph_id': 5, 'start_character': 711, 'end_paragraph_id': 5, 'end_character': 715, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '250462', 'title': 'San Francisco International Airport', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 836, 'bleu_score': 0.8421266985947291, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3725243029030931450}, 'section': 'Section::::History.\n'}]}]