Answer: A collection of pictures taken by photographers during the Civil War
Step-by-step explanation:
Primary sources are simply referred to as the original records during the time of a historic happening. It involves the records taken by the people that were at the exact place the historical event took place. Examples of primary sources are letters, maps, etc.
With regards to the options that are given, the example of primary source will be the collection of pictures taken by photographers during the Civil War.