Question: who is an a in pretty little liars
[{'answer': 'Mona Vanderwaal', 'provenance': [{'wikipedia_id': '25857222', 'title': 'Pretty Little Liars', 'start_paragraph_id': 1, 'start_character': 717, 'end_paragraph_id': 1, 'end_character': 732, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]