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The correct answer is D. They mapped trails and helped build forts

Explanation

Mountain men are a group of people who lived in the western mountains of the United States. These mountains were characterized by being difficult to access, so there were no roads in this area, and it did not have many human settlements. Once the idea of building and connecting the entire country was planted, the help of men who inhabited this area was needed to trace the roads and build them because they knew how to move and work on that terrain due to their extensive experience in that terrain. Therefore, the correct answer is D. They mapped trails and helped build forts

it is a better alternative

i believe

clean air is essential for health and survival

clean air provides nitrogen gas for plant respiration

clean air supplies oxygen that enables living organisms to breathe

hope this

i am brianly

sorry if this doesn't