Answer:
A) It gave Europe the message that the Western Hemisphere was no longer open for colonization.
Explanation:
The Monroe Doctrine established that any intervention by Europeans in the Americas would be seen as an act of aggression that would require intervention by the United States of America. The doctrine was presented by President Monroe during his sixth speech to Congress on the State of the Union. It was taken with doubts, at first, and then with enthusiasm. It was a decisive moment in the foreign policy of the United States. The doctrine was conceived by its authors, especially John Quincy Adams, as a proclamation by the United States of its opposition to colonialism in response to the threat posed by the monarchical restoration in Europe and the Holy Alliance after the Napoleonic wars.
