Question: rough endoplasmic reticulum is the site of synthesis of
[{'answer': 'protein', 'provenance': [{'wikipedia_id': '9775', 'title': 'Endoplasmic reticulum', 'start_paragraph_id': 2, 'start_character': 199, 'end_paragraph_id': 2, 'end_character': 206, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]