The Australian system of government is:

• A federal monarchy
• A parliamentary democracy
  Explanation:

  "The Australian system of government combines a federal structure, where power is shared between the national and state governments, with a parliamentary democracy, where citizens elect representatives to make laws. It is also a constitutional monarchy, meaning the King is the head of state, but his powers are limited by the Constitution and exercised by elected officials."
• A constitutional Monarchy
• Both B & C