A lot of JFK assassination theorists believe that which of the following is
true?
A. James Earl Ray killed JFK in 1963
B. JFK's wife was responsible for his death in 1963.
C. Organized crime killed JFK in 1963.

C

Explanation:

Organized crime killed JFK in 1963

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 governor can not veto a referendum that the voters approve