The correct answer is A) Many of the farmers on the Great Plains soon gave up because they could not farm the land.
The sentence from the article that best supports the thesis is "Many of the farmers on the Great Plains soon gave up because they could not farm the land.
The excerpt says that "human migration and population distribution can greatly alter or destroy the natural landscape..." So when American settlers traveled to the Great Plains, they got desperate because the land conditions for farming were not good. Human migration can affect the land when they settle in but do not have the conditions and do not take care of the land to maintain it in proper conditions to be farmed. People use raw materials and natural resources but do not do anything to repair them.
So now, for a thesis, you need to find a good thesis statement to capture the attention of the readers.