How did the United States acquire the area labeled number 4 on the map?
A. Mexico sold the territory to the U. S. in the Gadsden Purchase.
B. Mexico ceded the territory to the U. S. after the Mexican-American War.
C. The U. S. purchased Texas from Great Britain after the War of 1812.
D. The U. S. annexed Texas several years after it had gained its independence from Mexico.