What events have made gun violence a current major issue?

school shootings for the most part.

Explanation: due to the fact that many schools shootings have been happening, especially in america, gun violence has become a major issue that is hotly debated and protested.

School Shootings due to the fact that there have been hundreds only this year and weren’t not even half way through it.

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:

answer; people where able to travel across the u.s.a faster than any other mode of transportation,travel time was about a week,from coast to coast