What were two challenges american settlers faced moving west?

Indians and food shortage

D. People in present day Arizona constructed a large circle of red-earthern boulders is the correct answer.

Explanation:

Native Americans have been living in Arizona for thousands of years and it is the state with the largest number of Native American population. The Navajo Nation which is the largest American Reservation in the US and Tohno Oodham Nation, both are located in Arizona. There are twenty tribes which are the member of Inter-Tribal Council of Arizona. More than twenty-five percent area of the Arizona state is reserved for tribals.