Question: when did canada switch from gallons to litres
[{'answer': '1979', 'provenance': [{'wikipedia_id': '2732123', 'title': 'Metrication in Canada', 'start_paragraph_id': 5, 'start_character': 568, 'end_paragraph_id': 5, 'end_character': 572, 'bleu_score': 1.0, 'section': 'Section::::Conversion process.\n'}]}, {'provenance': [{'wikipedia_id': '2732123', 'title': 'Metrication in Canada', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 1316, 'bleu_score': 0.990171692033262, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9971637071886105417}, 'section': 'Section::::Conversion process.\n'}]}]