How might free movement across an internal border within the US be limited? A. A state might limit the types of plants and animals that can enter its borders. B. A state might pass a law limiting the number of citizens from other states that visit each year. C. A state might require a passport to enter its borders. D. A state might pass tariffs on goods that are imported.

The concept of free movement has already been common to the members of the European Union before it arrived in the United States. Every citizen coming to a member of the union has this freedom of movement in which it has the right to have access to the welfare system of a Euro member. In the case of the United States, the policy is applicable when the state might pass tariffs on goods that are imported.