It’s B, gaming territories by treaty or war. Let me explain:
Throughout the years mainly in the 1800s-1870s, the USA has numerous treaties and some wars that gained them the territory they have today. An example of a treaty is the Louisiana purchase of 1803, and a war example is the Mexican-American war, which gained them most of their territories out west.
The first answer is incorrect because the US mainly paid with their own money on these land purchases, and the last one is also incorrect because the US bought by the Louisiana territory, not sold it (and that would actually lose them territory).
Hope this helps! (Please consider branliest, because as of writing this post, I’m 5 away from the Virt rank, thanks!)
