Question: on what continents was the roman empire located at the height of its expansion
[{'answer': 'Europe', 'provenance': [{'wikipedia_id': '25507', 'title': 'Roman Empire', 'start_paragraph_id': 1, 'start_character': 164, 'end_paragraph_id': 1, 'end_character': 170, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Africa', 'provenance': [{'wikipedia_id': '25507', 'title': 'Roman Empire', 'start_paragraph_id': 1, 'start_character': 178, 'end_paragraph_id': 1, 'end_character': 184, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Asia', 'provenance': [{'wikipedia_id': '25507', 'title': 'Roman Empire', 'start_paragraph_id': 1, 'start_character': 194, 'end_paragraph_id': 1, 'end_character': 198, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]