HELP QUICKLY PLEASE!!! THE FIRST/RIGHT ANSWER GETS BRAINLIEST

The map above shows a portion of North America before the Mexican-American War. Which answer best explains how these boundaries changed as a result of the war?

A. Mexico and the United States split the disputed area approximately equally.

B. The United States gained the disputed area and nearly half of Mexico's territory.

C. Mexico gained the disputed area, but the United States kept the rest of their territory.

D.The United States gained the disputed area, but Mexico kept the rest of their territory.