Which statement describes a cause of the cuban missile crisis? a. the soviet union set up missiles in cuba and aimed them at the united states. b. the united states and cuba traded missiles to threaten the soviet union. c. the soviet union and cuba signed a treaty that banned missiles. d. castro sent missiles to russia to threaten the united states.

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.

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