Question: when did knotts berry farm became an amusement park
[{'answer': 'in 1968', 'provenance': [{'wikipedia_id': '176595', 'title': "Knott's Berry Farm", 'start_paragraph_id': 2, 'start_character': 481, 'end_paragraph_id': 2, 'end_character': 488, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]