Question: when did the ambulance service become part of the nhs
[{'answer': '1974', 'provenance': [{'wikipedia_id': '4944489', 'title': 'NHS ambulance services trust', 'start_paragraph_id': 3, 'start_character': 150, 'end_paragraph_id': 3, 'end_character': 154, 'bleu_score': 1.0, 'section': 'Section::::Areas.\n'}]}, {'provenance': [{'wikipedia_id': '4944489', 'title': 'NHS ambulance services trust', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 765, 'bleu_score': 0.983401048538667, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11535483396166543992}, 'section': 'Section::::Areas.\n'}]}]