Question: who plays the character a in pretty little liars
[{'answer': 'Janel Parrish', 'provenance': [{'wikipedia_id': '27998609', 'title': 'List of Pretty Little Liars characters', 'start_paragraph_id': 18, 'start_character': 69, 'end_paragraph_id': 18, 'end_character': 82, 'bleu_score': 1.0, 'section': 'Section::::Main characters.:Mona Vanderwaal.\n'}]}]