Question: how many artificial elements are in the periodic table
[{'answer': '24', 'provenance': [{'wikipedia_id': '29365', 'title': 'Synthetic element', 'start_paragraph_id': 1, 'start_character': 30, 'end_paragraph_id': 1, 'end_character': 32, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]