Question: brass is a mixture of what two metals
[{'answer': 'copper', 'provenance': [{'wikipedia_id': '3292', 'title': 'Brass', 'start_paragraph_id': 1, 'start_character': 21, 'end_paragraph_id': 1, 'end_character': 27, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'zinc', 'provenance': [{'wikipedia_id': '3292', 'title': 'Brass', 'start_paragraph_id': 1, 'start_character': 32, 'end_paragraph_id': 1, 'end_character': 36, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3292', 'title': 'Brass', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 310, 'bleu_score': 0.521594616550429, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 424499156390988845}, 'section': 'Section::::Abstract.'}]}]