Read the following passage carefully and choose the most appropriate answer to the question out of the four alternatives. When I think of my family's history on the land. I experience a pang of regret. Unlike much of the arid West, where the land has gone virtually unchanged for centuries, my place of origin, western Kansas, has been torn up by agriculture. The flat plains, excellent soil, and sparse but just adequate rainfall permitted farming; therefore farming prevailed, and a good 90% of the original sod prairie is gone. The consequence, in human terms, is that our relationship to our place has always felt primarily mercantile. We used the land and denied, or held at bay, its effect on us. Yet from my earliest childhood, when the most of the Kansas prairie was still intact, I 've known that the land also had a romantic quality. I've felt moved by the expanse of it , enthralled by size. I take pride in my identity as a plains daughter. What factor changed the entire landscape of Kansas?