What economic factors contributed to the settlement of the Oregon Country?

Due to the discovery of gold at Sutter's Mill, thousands of men traveled there to seek their own fortunes. Due to financial panics in the East, people were willing to move westward where there was fertile farmland available.

Explanation:

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: