Which of the following, if true, most undermines the argument's conclusion? A. In a study, the most effective anti-smoking advertisement featured a person smoking amidst a disapproving crowd. B. The most effective way to influence behavior is for parents to teach their children not to litter. C. People who watch public service advertisements are typically aware that actors are merely pretending to engage in the disapproved behavior. D. Teenagers are more likely to litter than the general population and less likely to be influenced by anti-litter advertisements. E. In a study, the most effective anti-littering advertisement featured a pristine public park with children playing in the background.