Why did the plains indians sign the treaty of fort laramie, which ceded some of their land to allow the passage of wagon trains?
a. they depended on trade with white settlers.
b. they wanted to protect their favored status with the u. s. government.
c. they believed it would them to displace weaker tribes.
d. they hoped to preserve their culture in the face of white onslaught?

The plain Indians sign the treaty of fort Laramie, which ceded some of their land to allow the passage of wagon trains because they were promised by the government that the remaining Indian land would remain untouched in the hopes that their culture may be preserved. But the effect was that they suffered extreme poverty, their culture and land was violated and was mainly ruled by outside bureaucrats.