President Woodrow Wilson's policy of strict neutrality during the early years of World War I was challenged by a German violations of freedom of the seas b the refusal of the League of Nations to supply peacekeepers c British disrespect for the Roosevelt Corollary d attacks by Mexicans on United States border towns

option d is correct. corroborated sources of historical evidence   is necessary to validate a claim about an event in history.

historians tend to use written sources, but audio and visual materials as well as artifacts are important objects that supply information to modern historians.

historical sources are usually divided into two categories: primary and secondary sources. depending on the historian's intent, some sources shift their designation. determining what type of sources toimplement, and the level of credibility and reliability of those sources, is a significant step in critical thinking for the historian.

explanation:

a. there was serious competition for tech jobs at the downtown clinic.

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