That last two and prolly the second one
Answer:
B
Explanation:
The Olympics brought people from all over the world that started to settle in.
(Brainliest?)
The correct answer should be Advances in Technology and Industrial revolution
Mexican-American war happened in the 40s so that's before 1860, while a war with Spain occurred in 1898 which is after the mentioned period. They did advance in technology exactly due to the industrial revolution. An agrarian revolution. An agricultural revolution didn't happen in the US because of the Long depression that slowed it all down.