The correct answer is B) New England states lost territory as people moved west.
What was not a way in which US boundaries changed between 1800 and 1821 was that "New England states lost territory as people moved west."
That never happened
What truly happened that doubled the size of the United States territory was the Lousiana Purchase in 1803. President Thomas Jefferson ordered the purchase of the territory that belonged to France. President Jefferson sent James Madison to Paris to accelerate negotiations and in April 1803, France accepted the prize of $11,250,000 to close the de deal.
New England states misplaced territory as human beings moved to the west. This isn't manner via way of means of America changed its boundaries. so the correct option is B.
The mainland of the united states of America is covered by the ocean Atlantic ocean in the east and the pacific ocean in western Canada in the north and Mexico in the south of the USA.
The US has changed its boundaries by purchasing of land like Florida from Spain, Louisiana purchased in 1803, and an agreement between Spain and England. The last time our boundaries changed was in 1961.
Therefore the correct option is B.
Learn more about US boundaries and history here:
brainly.com/question/538584