Question: what type of stone did the romans use
[{'answer': 'Marble', 'provenance': [{'wikipedia_id': '52685', 'title': 'Ancient Roman architecture', 'start_paragraph_id': 31, 'start_character': 0, 'end_paragraph_id': 31, 'end_character': 6, 'bleu_score': 1.0, 'section': 'Section::::Materials.:Stone.\n'}]}, {'answer': 'Travertine limestone', 'provenance': [{'wikipedia_id': '52685', 'title': 'Ancient Roman architecture', 'start_paragraph_id': 31, 'start_character': 530, 'end_paragraph_id': 31, 'end_character': 550, 'bleu_score': 1.0, 'section': 'Section::::Materials.:Stone.\n'}]}, {'answer': 'Other more or less local stones'}, {'provenance': [{'wikipedia_id': '52685', 'title': 'Ancient Roman architecture', 'start_paragraph_id': 31, 'start_character': 0, 'end_paragraph_id': 31, 'end_character': 793, 'bleu_score': 0.985238839858627, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3097592774853838405}, 'section': 'Section::::Materials.:Stone.\n'}]}]