The correct answer is C, the Supreme Court.
The Supreme Court of the United States is the highest court in the United States. This court has jurisdiction over a small range of cases, such as: disputes between two states, cases involving ambassadors and appellate jurisdiction over all state and federal court.
The Supreme Court consists of the Chief Justice of the United States and eight associate justices who are nominated by the President and confirmed by the Senate. The justices are appointed for life, unless they resign. Each justice has a single vote in deciding the cases argued before it.