Question: what was the first underground line in london
[{'answer': 'City & South London Railway', 'provenance': [{'wikipedia_id': '17839', 'title': 'London Underground', 'start_paragraph_id': 2, 'start_character': 275, 'end_paragraph_id': 2, 'end_character': 302, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '17839', 'title': 'London Underground', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 547, 'bleu_score': 0.8420452279440571, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16611719919480489597}, 'section': 'Section::::Abstract.'}]}]