Identify a true statement regarding unions in the United States. a. Private-sector employees are more likely to belong to labor unions than public-sector employees. b. Much of the decline of U.S. union membership can be attributed to the shift in U.S. jobs from service industries to manufacturing industries. c. Union workers frequently receive higher compensation than do nonunion workers. d. Unions have reduced efforts to organize white-collar workers because advances in technology have decreased their numbers in the workforce