Question: what is a beer keg made out of
[{'answer': 'aluminum or steel'}, {'provenance': [{'wikipedia_id': '1258772', 'title': 'Keg', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 275, 'bleu_score': 0.6280458351332731, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18352974443234111178}, 'section': 'Section::::Abstract.'}]}]