Question: who prevented the romans from sending embassies to the chinese
[{'answer': 'Parthians', 'provenance': [{'wikipedia_id': '1618577', 'title': 'Sino-Roman relations', 'start_paragraph_id': 1, 'start_character': 600, 'end_paragraph_id': 1, 'end_character': 609, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1618577', 'title': 'Sino-Roman relations', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 1244, 'bleu_score': 0.9899746208772191, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17249037285128546399}, 'section': 'Section::::Abstract.'}]}]