Which of the following is NOT covered by Social Security?

The correct choice highlights that railroad workers are generally covered by a different system than Social Security. Specifically, they are part of the Railroad Retirement Board (RRB), which administers benefits similar to those offered by Social Security but is designed specifically for railroad industry employees. This means that instead of contributing to Social Security, railroad workers pay into the RRB, allowing them to receive unique retirement and disability benefits tailored to the needs of those working in the railroad industry.

Conversely, self-employed workers, business owners, and insurance salesmen typically contribute to and are eligible for Social Security benefits, reflecting the diverse range of workers that the Social Security system is designed to support. Their contributions come from payroll taxes, which fund the Social Security program, ensuring they receive disability or retirement benefits when they meet certain criteria.