According to the passage, which one of the following is true of Carroll's study? A. It implies that right-to-work laws have had a negligible effect on workers in right-to-work states. B. It demonstrates that right-to-work laws have significantly decreased union membership from what it once was in right-to-work states. C. It argues that right-to-work laws have affected wages in right-to-work states. D. It supports the findings of most earlier researchers. E. It explains the mechanisms by which collusion between manufacturers and suppliers is accomplished.