Question: what is the natural abundance of ag−109
[{'answer': 'isotopes', 'provenance': [{'wikipedia_id': '2526968', 'title': 'Isotopes of silver', 'start_paragraph_id': 1, 'start_character': 62, 'end_paragraph_id': 1, 'end_character': 70, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2526968', 'title': 'Isotopes of silver', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 326, 'bleu_score': 0.9663744727315161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3572276890773629826}, 'section': 'Section::::Abstract.'}]}]