The Monroe Doctrine stated that the United States would

A. oppose European attempts to colonize nations.

B. encourage European attempts to colonize nations.

C. take control of existing European colonies.

D. interfere in European conflicts.

The right answer is: A) Oppose European ( ...) colonize nations. The Monroe doctrine, synthesized in the quote "America for the Americans", was elaborated by John Quincy Adams and attributed to president James Monroe in 1823. It established that any European intervention in America would be seen as an act of aggression that would require intervention of the United States of America. It was a decisive moment in the foreign policy of the United States representing its opposition to colonialism in response to the threat posed by the monarchical restoration in Europe and the Holy Alliance after the Napoleonic wars.