Which sentences, if added after sentence 12, would provide the most effective conclusion to support the author’s argument? (13)fans of the sport cannot continue to support a practice that leads to over 150 concussions every season. (14) consider a sound solution. (15)support the mandatory use of anti-concussion helmets. (13)if the nfl approves the regulation, it will demonstrate its commitment to the future of its players. (14)it’s about time that we all pull together and offer athletes more than "atta-boys" for the risks they take to entertain us. (15)after all, haven’t we moved past the time of gladiators? (13)although nfl players receive generous salaries, injured players can no longer fulfill their contracts. (14)often the effects of concussions prove to be more serious at later points in a player’s life. 15)it’s time for fans to assist players by supporting the regulated use of improved safety helmets. (13)will the availability of improved safety helmets guarantee that they will be used? (14) no, because many may think it fosters a less masculine image of physical strength. (15)by regulating their use, however, every player has a better option for his future.