Please help me if you can :) Review the map of the United States and think about what you know of the colonial period. What is one thing the Mississippi River, the Appalachian Mountains, and the Rocky Mountains all have in common?

A. They are all regions of intense cold and devastating storms that take human life.

B. They all offer important milestones for any journey into the western United States.

C. They all create rigid borders that affect the culture and trade of the people on either side of them.

D. They are all areas where great cultural shifts occur among Native American tribal groups.