Question: who won the last open at st andrews
[{'answer': 'Zach Johnson', 'provenance': [{'wikipedia_id': '18541861', 'title': 'List of The Open Championship champions', 'start_paragraph_id': 33, 'start_character': 12, 'end_paragraph_id': 33, 'end_character': 24, 'bleu_score': 1.0, 'section': 'Section::::Notes.\n'}]}]