The correct answer is B.
The Constitution enumerates certain powers which are reserved to the federal goverment and other powers which are delegated to the state.
Those powers which are not explicitly related in the document to any of the goverment levels will automatically be reserved to and exercised by the supreme federal goverment.
The correct answer is the Court of Appeals.
These Courts of Appeals are responsible for hearing the appeals from cases from the district courts. The Courts of Appeals, after hearing both sides of the story, are able to determine whether or not the case deserves to be overruled or brought before the Supreme Court. This helps to limit the amount of cases seen by the Supreme Court on a yearly basis.