Question: how many challenges does a coach get in the nfl
[{'answer': 'two opportunities per game', 'provenance': [{'wikipedia_id': '21373737', 'title': 'Replay review in gridiron football', 'start_paragraph_id': 6, 'start_character': 289, 'end_paragraph_id': 6, 'end_character': 315, 'bleu_score': 1.0, 'section': 'Section::::By league.:National Football League.\n'}]}, {'answer': 'a third challenge if both of the original two challenges were successful .'}, {'provenance': [{'wikipedia_id': '21373737', 'title': 'Replay review in gridiron football', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 501, 'bleu_score': 0.9766041382465441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3753128464578446997}, 'section': 'Section::::By league.:National Football League.\n'}]}]