The answer is A. <span>cultural diffusion</span>
It was one of America's best trading routes, it was used as a commercial, military, and immigrant trail. And then in 18-something they started building it into a train track... I think.
<span>city street lights. </span>
From what I can tell, the answer is <em><u>Muckraker.</u></em> These days, it's called "investigative" or "watchdog" journalism.
But yeah, a quick google search says that "the muckrakers were reform-minded journalists in the Progressive Era in the United States (1890's–1920's) who exposed established institutions and leaders as corrupt".
