How did social changes in the young nation open the door to opportunity for all Americans?

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:

chamberlains goal was to stop the uk ad germany from fighting which he went to hitler and asked if he could sign a peace treaty between germany and the uk

im not sure but i have a question for you?