Question: when was oil discovered in trinidad and tobago
[{'answer': '1857', 'provenance': [{'wikipedia_id': '30169', 'title': 'History of Trinidad and Tobago', 'start_paragraph_id': 50, 'start_character': 97, 'end_paragraph_id': 50, 'end_character': 101, 'bleu_score': 1.0, 'section': 'Section::::British period.:Discovery of oil.\n'}]}, {'provenance': [{'wikipedia_id': '30169', 'title': 'History of Trinidad and Tobago', 'start_paragraph_id': 50, 'start_character': 0, 'end_paragraph_id': 50, 'end_character': 646, 'bleu_score': 0.9349082726484861, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5087347314804646812}, 'section': 'Section::::British period.:Discovery of oil.\n'}]}]