Question: which metal does the word 'ferrous' refer to answer in words not symbols
[{'answer': 'iron', 'provenance': [{'wikipedia_id': '92523', 'title': 'Ferrous', 'start_paragraph_id': 1, 'start_character': 71, 'end_paragraph_id': 1, 'end_character': 75, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '92523', 'title': 'Ferrous', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 364, 'bleu_score': 0.55618711999189, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8689624340614202322}, 'section': 'Section::::Abstract.'}]}]