Which of the following is an example of secondary source?

A secondary source is created after an event, offering interpretation, analysis, or commentary on primary sources or historical events. An academic paper that analyzes a historical event exemplifies a secondary source because it involves the author's examination, evaluation, and synthesis of original materials or firsthand accounts.

In contrast, primary sources, such as a letter written by a historical figure or an original photograph, provide direct evidence or firsthand accounts of an event. They convey unmediated snapshots of the past. Similarly, while a film documenting a historical event can provide valuable insight, it would be categorized as a secondary source only if it includes creative or interpretive elements rather than being a direct recording of the event.