Question: what is the longest canal tunnel in uk
[{'answer': 'Huddersfield Narrow', 'provenance': [{'wikipedia_id': '1118434', 'title': 'Standedge Tunnels', 'start_paragraph_id': 2, 'start_character': 24, 'end_paragraph_id': 2, 'end_character': 43, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]