Question: what are the names of pluto's moons
[{'answer': 'Charon', 'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 133, 'end_paragraph_id': 1, 'end_character': 139, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Styx', 'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 141, 'end_paragraph_id': 1, 'end_character': 145, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Nix', 'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 147, 'end_paragraph_id': 1, 'end_character': 150, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Kerberos', 'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 152, 'end_paragraph_id': 1, 'end_character': 160, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Hydra', 'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 166, 'end_paragraph_id': 1, 'end_character': 171, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3048284', 'title': 'Moons of Pluto', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 336, 'bleu_score': 0.9663744727315161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7597296785609851021}, 'section': 'Section::::Abstract.'}]}]