Question: when did silk begin to be produced in china
[{'answer': '4000 and 3000 BC', 'provenance': [{'wikipedia_id': '10783723', 'title': 'History of silk', 'start_paragraph_id': 6, 'start_character': 179, 'end_paragraph_id': 6, 'end_character': 195, 'bleu_score': 1.0, 'section': 'Section::::Early history.:First appearance of silk.\n'}]}, {'provenance': [{'wikipedia_id': '10783723', 'title': 'History of silk', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 772, 'bleu_score': 0.9607526871878451, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5320485656709290426}, 'section': 'Section::::Early history.:First appearance of silk.\n'}]}]