The correct answer is D, as the Mexican-American War changed the boundary with Mexico to go mostly along the Rio Grande and the Gila River with a few streches on land in mostly New Mexico and California.
The Treaty of Cahuenga, signed on January 13, 1847 in Los Angeles, ended the disputes in California. The Mexican government initiated peace negotiations with the United States that culminated in the signing of the Treaty of Guadalupe Hidalgo, signed on February 2, 1848. The treaty granted the United States control over Texas, the disputed territory between Mexico and Texas that included all the land north of the Rio Grande and the territories known as Alta California and Santa Fe of New Mexico, including what now are the States of Arizona, California, Nevada, Utah, New Mexico and parts of Colorado, Wyoming, Kansas and Oklahoma (what is known as Mexican Cession).
