Question: which types of mutations are least likely to be subjected to natural selection
[{'answer': 'Neutral mutations', 'provenance': [{'wikipedia_id': '5542769', 'title': 'Neutral mutation', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 17, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '5542769', 'title': 'Neutral mutation', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 715, 'bleu_score': 0.9548377695433641, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9787600236390458754}, 'section': 'Section::::Abstract.'}]}]