Question: what type of rock is the twelve apostles
[{'answer': 'limestone stacks', 'provenance': [{'wikipedia_id': '145096', 'title': 'The Twelve Apostles (Victoria)', 'start_paragraph_id': 1, 'start_character': 39, 'end_paragraph_id': 1, 'end_character': 55, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]