Final answer:
The United States federal system of government fosters more interest groups because it has a large and diverse population with a wide range of interests. The correct option is B.
Step-by-step explanation:
The statement that best explains why the United States federal system of government fosters more interest groups than other systems of government is (b) The United States has a large and diverse population, which creates a wide range of interests that are represented by interest groups.
The United States has a population of over 300 million people, coming from different backgrounds, cultures, and regions. This diversity leads to a wide range of interests and perspectives that are represented by interest groups. These groups advocate for specific issues and policies that align with the interests of their members.
For example, there are interest groups representing environmental conservation, labor rights, gun control, and many other issues. The size and diversity of the population in the United States provide a fertile ground for the formation of numerous interest groups.