Please help me i need this answered fast

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain

explanation:

the addition to geographic boundaries that might have  kept the people of the huang river civilization from traveling to far distance region is that they had learned about the other river valley civilizations but feared contact would bring invasion.

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for hobos it was a very hard time most hid on the sides of the railroad tracks causing people to get bulls and get them off sometimes causing in fatal death they couldnt get people to give them money because the   people were also in need of money