Question: what is one of the greatest structural achievements of the bronze age
[{'answer': 'the corbelled arch', 'provenance': [{'wikipedia_id': '12527374', 'title': 'History of construction', 'start_paragraph_id': 11, 'start_character': 22, 'end_paragraph_id': 11, 'end_character': 40, 'bleu_score': 1.0, 'section': 'Section::::Copper Age and Bronze Age construction.\n'}]}, {'provenance': [{'wikipedia_id': '12527374', 'title': 'History of construction', 'start_paragraph_id': 11, 'start_character': 0, 'end_paragraph_id': 11, 'end_character': 351, 'bleu_score': 0.96746874041754, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9663124221775289588}, 'section': 'Section::::Copper Age and Bronze Age construction.\n'}]}]