Final answer:
A primary source is a firsthand account of an event by someone who witnessed it. A diary entry from someone who lived during the period being studied qualifies as a primary source because it is an original document offering firsthand testimony valuable for historical analysis.
Step-by-step explanation:
An example of a primary source is an account by a person who witnessed an event, providing a direct connection to the historical period in question. Among the options provided, a diary entry by a person who lived in the period under discussion is a representative example of a primary source. This is because it constitutes an original document that offers firsthand testimony, commonly valued by historians for building a clear and accurate picture of the past.
Primary sources may include personal narratives, eyewitness accounts, and original documents such as treaties, speeches, and newspaper coverage of events as they occurred. These primary data sources are invaluable as they are created contemporaneously with the events they describe, providing the most immediate connection to the subject of study.
In contrast, secondary sources are created after the event and provide interpretation or analysis of the primary sources. Understanding the difference between primary and secondary sources is essential for conducting rigorous historical research and analysis.