Question: what is the name of the boundary between the mantle and the outer core
[{'answer': 'core -- mantle boundary'}, {'provenance': [{'wikipedia_id': '1431559', 'title': 'Core–mantle boundary', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 968, 'bleu_score': 0.526108052546506, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1713360945777238206}, 'section': 'Section::::Abstract.'}]}]