Because a primary source is an original document or other material that has not been changed in any way. It is a reliable first-hand account usually written at or near the time the event(s) occurred. Usually it was produced by someone with direct personal knowledge of the events that are described.
The answer is A..... a primary source was present during an experience or time period. An example is an original document. A secondary source interprets and analyzes primary source. An example is a textbook, magazine or an article.
