Question: mt. rushmore is composed of which type of rock
[{'answer': 'granite', 'provenance': [{'wikipedia_id': '185973', 'title': 'Mount Rushmore', 'start_paragraph_id': 1, 'start_character': 76, 'end_paragraph_id': 1, 'end_character': 83, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '185973', 'title': 'Mount Rushmore', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 642, 'bleu_score': 0.521038167793317, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17276040817026388748}, 'section': 'Section::::Abstract.'}]}]