Answer:
D. religious principles and beliefs
Step-by-step explanation:
D is correct answer because it is a form of government that exist today in Vatican and Saudi Arabia. In these countries religion and religious laws are above secular.
A is wrong because those governments are constitutional monarchies. They have Constitution as the most important legal act. We have the example of Sweden today.
B is usually called parliamentary monarchy, the example of Britain.
C is wrong because it would be like in the case of United States, some type of federacy.