Final answer:
The correct answer is a. union shop agreement, which requires employees to join the labor union as a condition for employment. This type of agreement has declined but can still be found in certain industries.
Step-by-step explanation:
A union shop agreement is a contractual agreement where an employer requires employees to join the union as a condition for their employment. This type of arrangement ensures that all workers are members of the labor union and contribute to the collective bargaining process. Labor unions negotiate with employers over compensation and work conditions on behalf of the workers. This system played an integral role in protecting worker rights and improving workplace conditions.
However, the prevalence of such agreements has declined alongside union membership in the United States. Economic shifts from manufacturing to service industries, globalization, worker-friendly legislation, and laws less favorable to organizing unions have contributed to this decline. Today, a smaller percentage of the workforce is unionized compared to the peak levels in the mid-20th century. Despite the decrease in union shop agreements, they are still found in certain industries where union membership remains significant.