Outside powers should not attempt to interfere with affairs in the Western Hemisphere (that rhymed). They should not set up colonies or attempt to overthrow newly independent republics. This would be considered 'dangerous to our peace and safety.' The principles define what?

Monroe Doctrine.

Explanation:

Monroe Doctrine is the name given to the principle stated by President James Monroe in his speech to Congress in 1823. Many Latin American countries were gaining their independence from Spanish and Portuguese Empires in the 1920s.

So Monroe in his speech on December 2, 1823, to the Congress, expressed that the New World and the Old World need to remain aloof and any interference from European country would be considered a hostile act. This principle was later named the Monroe Doctrine in the 1850s that became a keystone of the United States' foreign policy.

Thus the correct answer is Monroe Doctrine

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."