Question: who does bart's voice on the simpsons
[{'answer': 'Nancy Jean Cartwright', 'provenance': [{'wikipedia_id': '113158', 'title': 'Nancy Cartwright', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 21, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '113158', 'title': 'Nancy Cartwright', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 325, 'bleu_score': 0.9287747521948501, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18207258765892990067}, 'section': 'Section::::Abstract.'}]}]