第六段第二句提到“Merchants in America’s eastern cities used it to gather information…”，对应选项A的内容。根据该段第三句提及的“In the American debate about slavery, it offered abolitionists a low-cost way to spread their views, just as later technologies have cut the cost and widened the scope of political lobbying”，可知选项B（低成本传播思想）和选项C（促进政治游说）都与原文相符。