Question: who sings the song for a thousand years
[{'answer': 'Christina Perri', 'provenance': [{'wikipedia_id': '33545013', 'title': 'A Thousand Years (Christina Perri song)', 'start_paragraph_id': 0, 'start_character': 18, 'end_paragraph_id': 0, 'end_character': 33, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]