Mountains and seas brought the greek city states together

the decreasing neutrality of the u. s. in world war i

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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:

the crusades are one of the most significant events in the history of europe and the middle east.   they were a series of religious wars carried out by christian crusaders from europe during the timeframe of the middle ages.   beginning in 1095 ce, the crusades saw european knights and noblemen travel to the middle east in an attempt to capture the holy land away from muslim people that had controlled the region for the previous centuries.   the term crusade means ‘cross’.   therefore, the europeans that became crusaders viewed themselves as ‘taking up the cross’.   in fact, many of the crusaders wore crosses on their clothing and armor as they made their pilgrimage to the holy land.

explanation:

d. direct