Answer:
The statement that describes a similarity between source 1 and source 2 is:
C. Both are primary sources.
Both source 1 (Abraham Lincoln's speech during the seventh debate with Stephen A. Douglas) and source 2 (a letter written by a soldier during the Civil War) are primary sources, as they are original sources of information that were created at the time of the events they describe. In contrast, secondary sources are interpretations or analyses of primary sources that are created after the fact, such as textbooks or historical analyses.