Question: what law freed all slaves in the united states
[{'answer': 'the 13th amendment', 'provenance': [{'wikipedia_id': '9515', 'title': 'Emancipation Proclamation', 'start_paragraph_id': 1, 'start_character': 698, 'end_paragraph_id': 1, 'end_character': 716, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '9515', 'title': 'Emancipation Proclamation', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 931, 'bleu_score': 0.948991299858662, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 964366893612467594}, 'section': 'Section::::Abstract.'}]}]