Answer:
C. The king mistreated the citizens.
Step-by-step explanation:
The Roman monarchy was overthrown around 509 BCE, during a political revolution that resulted in the expulsion of Lucius Tarquinius Superbus, the last king of Rome.
Despite waging a series of successful campaigns against Rome's neighbors, securing Rome's position as head of the Latin cities, and engaging in a series of public works, Tarquin was a very unpopular king due to his violence and abuse of power.
For this reason, we can conclude that the right answer is the letter C.