Question: what feature led to the most sales for the playstation 2
[{'answer': 'backwards compatibility', 'provenance': [{'wikipedia_id': '15822958', 'title': 'PlayStation 2', 'start_paragraph_id': 2, 'start_character': 35, 'end_paragraph_id': 2, 'end_character': 58, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '15822958', 'title': 'PlayStation 2', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 557, 'bleu_score': 0.6364296516846181, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1850296262877838032}, 'section': 'Section::::Abstract.'}]}]