We’re the tycoons of the industrial revolution captions of the industry or robber barons

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 correct answer is:   the domino theory states that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.

you didn't post an image.