15. Why was World War I a war of attrition? O A. It was a war that was characterized by revolutions and disorder.

O B. It was a war that was fought on a global scale.

O C. It was a war marked by new military technologies such as machine guns, tanks, and airplanes.

O D. It was a war in which adversaries were worn down by a continuous loss of life and resources.

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: