Answer: B
Explanation: A tyrant is basically a dictator. The definition of dictator is someone who isn't lawfully in power. In this scenario answer b is the best option because all the power is being given to the emperor who can make whatever rules he wants. The reason c isn't the answer is because the queen's power is limited. In my opinion I would phrase answer b a little differently because technically it's a monarchy rather than a tyranny since the emperor is usually the lawful heir, but in this case b would make the most sense.
