Question: who was the ruler of the aztec empire when the spanish conquest began
[{'answer': 'emperor Cuauhtemoc', 'provenance': [{'wikipedia_id': '5865939', 'title': 'Spanish conquest of the Aztec Empire', 'start_paragraph_id': 2, 'start_character': 442, 'end_paragraph_id': 2, 'end_character': 460, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '5865939', 'title': 'Spanish conquest of the Aztec Empire', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 670, 'bleu_score': 0.750499274405344, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11379406679661728861}, 'section': 'Section::::Abstract.'}]}]