Question: when did uk change from gallons to litres
[{'answer': '1994', 'provenance': [{'wikipedia_id': '12882', 'title': 'Gallon', 'start_paragraph_id': 30, 'start_character': 187, 'end_paragraph_id': 30, 'end_character': 191, 'bleu_score': 1.0, 'section': 'Section::::Worldwide usage of gallons.\n'}]}]