Congress has 4 ways to check the power of the Supreme Court. Legialatively they can pass new laws or by the ammendment process change the constitution. The other checks are they can adjust the size of the court, impeachment of Justices and the confirmation process of the Court justices.
D. Lack of a clearly designated successor to the imperial throne. During the decline of the empires, the succession of the throne became a contest between family members. Hope this helps.
