Question: who sang the theme song from the movie arthur
[{'answer': 'Christopher Cross', 'provenance': [{'wikipedia_id': '2626012', 'title': "Arthur's Theme (Best That You Can Do)", 'start_paragraph_id': 1, 'start_character': 105, 'end_paragraph_id': 1, 'end_character': 122, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2626012', 'title': "Arthur's Theme (Best That You Can Do)", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 781, 'bleu_score': 0.9680991184556271, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11693687288862968562}, 'section': 'Section::::Abstract.'}]}]