Question: which bone is located at the base of the skull
[{'answer': 'Ethmoid bone', 'provenance': [{'wikipedia_id': '13428778', 'title': 'Base of skull', 'start_paragraph_id': 6, 'start_character': 12, 'end_paragraph_id': 6, 'end_character': 24, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Bones.\n'}]}, {'answer': 'Temporal bone', 'provenance': [{'wikipedia_id': '13428778', 'title': 'Base of skull', 'start_paragraph_id': 10, 'start_character': 12, 'end_paragraph_id': 10, 'end_character': 25, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Bones.\n'}]}, {'answer': 'Frontal bone', 'provenance': [{'wikipedia_id': '13428778', 'title': 'Base of skull', 'start_paragraph_id': 9, 'start_character': 12, 'end_paragraph_id': 9, 'end_character': 24, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Bones.\n'}]}, {'answer': 'Sphenoid bone', 'provenance': [{'wikipedia_id': '13428778', 'title': 'Base of skull', 'start_paragraph_id': 7, 'start_character': 12, 'end_paragraph_id': 7, 'end_character': 25, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Bones.\n'}]}, {'answer': 'Occipital bone', 'provenance': [{'wikipedia_id': '13428778', 'title': 'Base of skull', 'start_paragraph_id': 8, 'start_character': 12, 'end_paragraph_id': 8, 'end_character': 26, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Bones.\n'}]}]