To determine which response matches a current state with the corresponding historical area:
A. Utah: Oregon Territory - Incorrect. Utah is part of the area that was part of the Mexican Cession, while the Oregon Territory mainly includes parts of Oregon, Washington, and some parts of Idaho and Montana.
B. Arizona: Mexican Cession - Correct. Arizona was indeed part of the territory ceded to the United States from Mexico after the Mexican-American War.
C. Colorado: Gadsden Purchase - Incorrect. The Gadsden Purchase is an area that mostly includes parts of southern Arizona and New Mexico, not Colorado.
D. Washington: Louisiana Purchase - Incorrect. Washington was not part of the Louisiana Purchase; it was primarily part of the Oregon Territory.
Therefore, the correct response is:
B. Arizona: Mexican Cession.