The answer is C. the main point an author plans to prove in a piece of writing.
hope this helps
it was a mix of A. B. C. just not slaves, slaves weren't a huge until the late 1690's.
The main way in which the railroads contributed to the end of the large buffalo herds was that "The railroad tracks were obstacles that the buffalo would not cross". It sounds silly, but the buffalo actually refused to cross the tracks for reasons that are still misunderstood.<span />
