Lines 1-15 clearly outline why answer choice (B) is the correct answer. We see that during the first 25 years of the Dawes Act, Native Americans could use but not sell their land and after the 25-year period they would receive a "fee patent" awarding full legal ownership of the land.
So, only after the first 25 years were they allowed to sell the land, i.e. Answer choice (B).
Hope that helps! Please let us know if you have any other questions.
