What Is the Unitary State Assumption

What is the unitary state assumption?

A) The belief that a state's leaders have the most impact on foreign policy decisions.
B) The examination of states that do not have a federal system of government.
C) The supposition that states act as if they have a unitary,rather than a federal,system of government.
D) The treatment of states as coherent actors with a set of interests that belong to the state.
E) The belief that one domestic actor can control the foreign policy of a state.