Final answer:
The current mandatory retirement age in the United States is D) none. However, the full retirement age has increased from sixty-five to sixty-seven for workers born after 1959.
Step-by-step explanation:
The current mandatory retirement age in the United States is none.
Originally, the full retirement age was set at sixty-five, but changes in legislation have increased it to sixty-seven for workers born after 1959. The age of eligibility for full retirement benefits was increased from 65 to 66 in 1983, but the change didn't take effect until 2009. The age will gradually increase to 67 in 2027.