Question: when did the use of iron began in the subcontinent
[{'answer': 'during the 2nd millennium BC', 'provenance': [{'wikipedia_id': '14711', 'title': 'Iron Age', 'start_paragraph_id': 26, 'start_character': 121, 'end_paragraph_id': 26, 'end_character': 149, 'bleu_score': 0.668740304976422, 'section': 'Section::::Ancient Near East.\n'}]}]