The policy of the Roosevelt Corollary is best seen in

Question 3 options:

The beginning of World War 2

England declaring war on the US in 1905

the US warning European interference in Latin America would lead to US intervention

the US invading Mexico and Panama in response to political uprisings

The answer is option 3: The US warning European interference in Latin America would lead to US intervention

The Roosevelt Corollary established that the United States would work as an international police power to the Western Hemisphere (Latin America), therefore if there existed any conflict between the European countries and Latin American countries, the United States would intervene to enforce legitimate claims (large debts, civil unrest, etc) of European, rather than having the Europeans press their claims directly.

Answer: The US warning that European interference in Latin America would lead to US intervention.

Details:

The Roosevelt Corollary was set forth by President Theodore Roosevelt in 1904 (in his State of the Union Address that year). It was a tweaking of the Monroe Doctrine. The Monroe Doctrine expressed US opposition to European interference in the Americas. Roosevelt's corollary to that doctrine was that the United States would intervene in conflicts between European countries and Latin American countries, rather than having the Europeans press their claims directly.