This text excerpt explains a study done on football players who had concussions and those who did not. The study found there was no difference in how fast or accurately the players answered questions. However,
A there was no difference in general medical costs for the players.
B the brains of players who had concussions had to work harder to complete the memory test tasks.
C the players with concussions also struggled in their classes.
D the brains of players who did not have concussions also showed greater levels of happiness.