Question: who chaired the constitutional convention in philadelphia in 1787
[{'answer': 'George Washington to preside'}, {'provenance': [{'wikipedia_id': '1743283', 'title': 'Constitutional Convention (United States)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 734, 'bleu_score': 0.625604184691518, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14812828742625344452}, 'section': 'Section::::Abstract.'}]}]