What force is causing this phenomena

Which of the following statements accurately describe the importance of the american concept of government and democracy? (select all that apply.)

How does the principle of federalism affect the u.s. government? a. it guarantees that the united states will always be a representative democracy b. it ensures that the state governments have greater authority that the federal government c. it creates both separate and overlapping powers for the federal and state governments d.it divides the federal and state governments into three branches

How have people adapted physically to different environments? why do you think these differences developed?