Recall that phillippe leyens and his colleagues (1975, 1977) exposed different groups of children to a steady diet of violent films over a relatively long period. these researchers found thata. a single exposure can result in as much aggression as a long exposure. b. the relationship between exposure and aggression holds for boys, but not for girls. c. with prolonged exposure, even nonaggressive children can become more aggressive. d. rewards for cooperation can reduce the effects of exposure to violence.