Which accurately describes a chart developed 20 years after a historical event?
a. effective secondary source document
b. too biased for historical evidence
c. too focused for historical evidence
d. unreliable narrative source
e. useful primary source document

The correct answer is a.effective secondary source document. Secondary sources are sources that talk about and analyze a historical event from the perspective and the understanding of the writer or the scientific community. It's not like pictures or journals that would be primary, but rather this is an analysis of events that comes after the events have happened.