Final answer:
The United States Supreme Court in Roper v. Simmons (2005) ruled that individuals under the age of 18 at the time of their crime cannot be subjected to the death penalty, setting the threshold at 18 years old. option (B)
Step-by-step explanation:
In the landmark case Roper v. Simmons (2005), the United States Supreme Court made a significant ruling regarding the death penalty. Specifically, in this case, the Supreme Court held that the death penalty may not be imposed on those who were under the age of 18 when they committed a crime. Therefore, the correct answer to the question is that after Roper v. Simmons, the age set by the Supreme Court for imposing the death penalty is 18 years old.
This decision reflects the Court's stance on the Eighth Amendment, which prohibits cruel and unusual punishment. The Court determined that executing individuals who were minors at the time of their offense is unconstitutional. The ruling is a part of a series of decisions that highlight the narrowing application of the death penalty, which also includes protections for defendants with intellectual disabilities and sanctions against executing individuals for crimes that did not result in the death of another person.