Answer:
in 1846, a dispute over the border between Texas and Mexico resulted in armed conflict, and the Mexican–American War began. After offering to buy the territory, Polk moved U.S. troops into a place that Mexico said was not in Texas, but rather part of the Mexican state of Coahuila. The Mexican army attacked them.
Explanation:
The answer to your question is,
A. Railroad operations across the nation
-Mabel <3
Introduces and explains the purpose of the U.S. Constitution
