Question: which version of windows introduced the metro user interface
[{'answer': 'Windows Phone 7', 'provenance': [{'wikipedia_id': '28305156', 'title': 'Metro (design language)', 'start_paragraph_id': 13, 'start_character': 83, 'end_paragraph_id': 13, 'end_character': 98, 'bleu_score': 1.0, 'section': 'Section::::Reception.:Before Windows 8.\n'}]}, {'provenance': [{'wikipedia_id': '28305156', 'title': 'Metro (design language)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 977, 'bleu_score': 0.9362893250854851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6883933776831989108}, 'section': 'Section::::Abstract.'}]}]