Question: what led to the end of indus valley civilization
[{'answer': 'drought', 'provenance': [{'wikipedia_id': '46853', 'title': 'Indus Valley Civilisation', 'start_paragraph_id': 108, 'start_character': 30, 'end_paragraph_id': 108, 'end_character': 37, 'bleu_score': 1.0, 'section': 'Section::::Late Harappan.:"Aryan invasion".\n'}]}, {'answer': 'decline in trade with Egypt and Mesopotamia'}, {'provenance': [{'wikipedia_id': '46853', 'title': 'Indus Valley Civilisation', 'start_paragraph_id': 109, 'start_character': 0, 'end_paragraph_id': 109, 'end_character': 327, 'bleu_score': 0.8842429471030611, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15743480646888977501}, 'section': 'Section::::Late Harappan.:Climate change and drought.\n'}]}]