Question: where does an atom's mass come from
[{'answer': 'protons and neutrons', 'provenance': [{'wikipedia_id': '19604151', 'title': 'Atomic mass', 'start_paragraph_id': 1, 'start_character': 206, 'end_paragraph_id': 1, 'end_character': 226, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19604151', 'title': 'Atomic mass', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 447, 'bleu_score': 0.6915701935864731, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8403327616082733060}, 'section': 'Section::::Abstract.'}]}]