Question: the minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction
[{'answer': 'critical mass', 'provenance': [{'wikipedia_id': '22133', 'title': 'Nuclear chain reaction', 'start_paragraph_id': 14, 'start_character': 100, 'end_paragraph_id': 14, 'end_character': 113, 'bleu_score': 1.0, 'section': 'Section::::Fission chain reaction.:Nuclear fission fuel.\n'}]}, {'provenance': [{'wikipedia_id': '22133', 'title': 'Nuclear chain reaction', 'start_paragraph_id': 14, 'start_character': 0, 'end_paragraph_id': 14, 'end_character': 320, 'bleu_score': 0.9603762111511761, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4412617592155262646}, 'section': 'Section::::Fission chain reaction.:Nuclear fission fuel.\n'}]}]