Question

the social security administration faces new challenges in the twenty - first century because
there are more workers paying into the system.
its services are no longer needed by american workers.
there are a greater number of retirees in the system.
its revenues are needed in other government programs.

Explanation:

Social Security relies on current workers' contributions to fund retiree benefits. In the 21st century, the aging population has led to a larger number of retirees drawing benefits, while the ratio of working-age people to retirees has declined, creating strain on the system. The other options are incorrect: more workers paying in would help, not challenge; the services are still needed by workers and retirees; and while funds may be redirected in some cases, this is not the core structural challenge.

Answer:

there are a greater number of retirees in the system.