Question: who did viswanathan anand defeat in 2012 to retain the world chess champion title
[{'answer': 'Boris Gelfand', 'provenance': [{'wikipedia_id': '17189128', 'title': 'World Chess Championship 2012', 'start_paragraph_id': 1, 'start_character': 120, 'end_paragraph_id': 1, 'end_character': 133, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '17189128', 'title': 'World Chess Championship 2012', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 481, 'bleu_score': 0.97451705556073, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2174243166169144356}, 'section': 'Section::::Abstract.'}]}]