American voter turnout is lower due to the decline in all of the following EXCEPT

Which of the following statements is true of labor unions?

A. In the private sector, it is compulsory for workers to join unions. B. It is much easier to form and maintain unions in the United States than in most other industrial nations. C. Most business owners in the United States make enormous efforts to ensure that their own businesses are unionized. D. Today, members of organized labor make up more than 30 percent of all wage and salary workers. E. The political power of labor unions has waned over the last several decades.

Because social and policy research is difficult to pin down, researchers often employ multiple methods to confirm their findings, an approach called _______________.

Fill in the blank(s) with the appropriate word(s).