When World War II Ended, Soldiers Came Home, and a Demographic

When World War II ended, soldiers came home, and a demographic "baby boom" began nine months later. That postwar generation began drawing Social Security and Medicare benefits around 2010. How does this affect mandatory spending?

A) no effect because Social Security and Medicare require discretionary spending
B) no effect because Social Security and Medicare are regulatory programs
C) decreases it because baby boomers no longer draw on mandatory education and worker training programs
D) increases it because the number of people demanding mandatory benefits is increasing