Answer: a. Isolationism refers to a foreign policy approach where a country avoids involvement in international affairs and avoids forming alliances. Diplomacy involves negotiating and communicating with other countries to resolve conflicts and maintain peace. Intervention refers to the use of military or economic power to interfere in the affairs of another country. Imperialism involves the colonization or control of other countries and territories for economic gain.
b. In the document, McKinley states that he believes in a policy of benevolent assimilation in the Philippines. This approach involves taking control of the Philippines to "civilize and Christianize" the population, while also providing protection and economic benefits. This approach can be seen as a form of imperialism, as the United States was seeking to control and influence the Philippines for their own purposes.
c. An event that caused a change in U.S. foreign policy in the period 1890-1910 was the Spanish-American War. The war marked the first time that the United States became involved in overseas imperialism and marked a shift towards a more interventionist foreign policy. The victory in the war gave the United States control over Puerto Rico, Guam, and the Philippines, leading to a significant expansion of American territorial and economic influence.