Final answer:
Among the provided options, Iran is an example of a theocracy. A theocracy is a government system where religious leaders rule in the name of a divine authority and have significant influence over the state's laws and policies.
Step-by-step explanation:
A theocracy is a form of government where religious leaders control the state, ruling under a divine guidance or with the belief that they are divinely guided. Among the options provided (The United States, Brazil, Russia, Iran), Iran is considered a theocracy.
The United States operates under a system of separation between religion and state, while Iran integrates religious dogma directly into its governance, with the religious hierarchy controlling the state's administrative hierarchy. This is seen in the influence of Islamic law on its civil and political structures.