A historical source is valid when it:
A. was written by a person who observed an event.
What is a historical document?
This is the term that is used to describe a particular document that tells us of the trail of events that have occurred in the past. That is the events that have the timeline of having happened over a long period of time.
They are most valid when the event is being talked about by a person that has first hand knowledge of what happened instead of telling stories of what they heard.
Read more on historical documents here: https://brainly.com/question/228934
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