The correct answer is they blazed trails through the Rocky Mountains and other difficult terrain.
Mountain men were people who lived in the wild of Rocky Mountains from 1810 to 1880. These men played an important role in <em>creating roads</em> so people from the East could travel to the West, helping the fur companies improve their trade. Many mountain men worked as a <em>“free trappers”</em>(by their own), but a lot of them were hired by fur companies.
What is what cause there is no meaning for it?.
I'm pretty sure they were called Hieroglyphs, and they were drawn on walls. They usually depicted animals, pharaohs, and they told stories. Sometimes they told stories of legends the Egyptians believed in. I hope this helps.