In what way is the concept of rule of law applied to the branches of the federal government?

To me, the rule of law indicates that no man or woman is above the law. That the process works for everyone.
So, A is the best answer.
If no person, or branch of Government, is above the law, how do you structure a system that makes that theory a reality? You would need separation of powers to ensure that no one branch has ALL the power.