Question: when was the clean air act passed in the uk
[{'answer': '1956', 'provenance': [{'wikipedia_id': '1591735', 'title': 'Clean Air Act 1956', 'start_paragraph_id': 0, 'start_character': 14, 'end_paragraph_id': 0, 'end_character': 18, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1591735', 'title': 'Clean Air Act 1956', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 280, 'bleu_score': 0.827140336932013, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6602930848302158761}, 'section': 'Section::::Abstract.'}]}]