Question: name of stone which never sink in water
[{'answer': 'Pumice', 'provenance': [{'wikipedia_id': '230364', 'title': 'Pumice', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 6, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '230364', 'title': 'Pumice', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 360, 'bleu_score': 0.9357293803829071, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6804907423799624697}, 'section': 'Section::::Abstract.'}]}]