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.

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.

i dont know sorry why dont you looking it up on google

50% i think

explanation: