What was the importance of the monroe doctrine?

a. it supported labor laws and collective bargaining.

b. it prevented european colonization and intervention in the western hemisphere.

c. the doctrine prevented militarism in the western hemisphere.

I believe the answer is B.

Because the Monroe Doctrine stated that, the newly independent United States would not tolerate European powers interfering with the nations in the Western Hemisphere, and if the European powers did interfere, then the United States would retaliate with war.