Your answer would be C, mainly because the soil near a waterway is very fertile, and before cars, boats were a cheap, easy way of transit.
History is his story I think that's the answer. Just playing though
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.
Answer:
They lost the Mandate of Heaven
Explanation: