Question: what college has produced the most nfl quarterbacks
[{'answer': 'Purdue', 'provenance': [{'wikipedia_id': '22171747', 'title': 'Quarterback U', 'start_paragraph_id': 2, 'start_character': 72, 'end_paragraph_id': 2, 'end_character': 78, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '22171747', 'title': 'Quarterback U', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 441, 'bleu_score': 0.972407137066537, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 337794204752109651}, 'section': 'Section::::Abstract.'}]}]