Question

The United States bought Alaska in 1867 to

keep Russia from expanding toward the US mainland.
stop other countries from taking over the territory.
control the territory’s abundance of resources.
open a critical trade route with the Far East.

Answer 1

stop other countries from taking over the territory.

(The U.S. bought Alaska in part to remove Russia as a rival presence in North America and to keep Britain or other powers from acquiring it.)