What Principle Was Stated in the Decision for the Case

What principle was stated in the decision for the case Duncan v. Louisiana?

A) States must provide trial by jury as an option for anyone accused of a capital crime.
B) States have autonomy from the federal government. As such, they are not held to the Constitutional requirement that governments must provide jury trials.
C) States, like the federal government, must provide trial by jury to ensure the proper delivery of justice.
D) Although the states have this requirement, the federal government does not have to provide a trial by jury to an accused person.
E) The federal government must try any case that could potentially punish the defendant with more than six months of imprisonment.