What is the relationship between the federal government and state governments?

A
All state governments are structured exactly the same as the federal government.
B
State governments are in place to enforce the federal government's authority in each state.
C
State governments have power over specific issues that the federal government does not.
D
All state governments have three branches, but they do not function the same as the federal government.

the Relationship between Federal and State Government. In the United States, the government operates under a principle called federalism. Two separate governments, federal and state, regulate citizens. The federal government has limited power over all fifty states

(d) rivers.

explanation:

civilizations developed around rivers because their waters provided places to hunt and fish. also, as the rivers flooded, the lands around them became fertile. this allowed them to support farming. this is especially true of the nile river, which flooded the same time each year.