The correct answer is - B. federal.
The United States is one of the largest countries in the world, and also the most powerful country in the world in most of the things. But unlike most of the countries, the United States are a country made out from fifty entities, or rather fifty federal states, thus making the country a federal state. Despite all federal states being under the same flag and same government, still, all of them have the right to create their own laws, to implement some or cut off some, in accordance to their own interest.
