Read this passage which source is related to the 1858 debates between Stephen A Douglas and Abraham Lincoln as they Campaign for a seat in the United States Senate.

Source One
Over 150 years ago Abraham Lincoln and Stephen A Douglas Held 7 debates us a campaign for a senate seat in Illinois. the debates focused on the issue of slavery and its expansion into the territories. Douglas helped overturn the prohibition on slavery in the territories of Kansas and Nebraska with the Kansas Nebraska Act. Referred to as popular sovereignty, It meant that's the sense in Kansas and Nebraska, not the federal government, could determine whether slavery should be allowed to exist in these territories.

Source 2
This is the real issue [with the question of slavery]... It is the eternal struggle between these two principles- right and wrong- throughout the world. They are the two principles that have stood face-to-face from the beginning of time; and will ever continue to struggle. The one is the common right of humanity and the other two divine right of kings. It is the same principle in whatever shape it develops is self it is the same spirit that says, “you work and toil and in bread, and I'll eat it.” No matter and what shape it comes, weather from the mouth of a king who seeks to bestride the people of his own nation and there by the fruit of thy labor, or from One race of meds as an apology for enslaving another race, it is the same tyrannical principle.
-Abraham Lincoln, during the seventh debate with Stephen A Douglas

Which statement describes a common feature of these sources?
A. Both indicate that Douglas's opinions on race were the opposite of Lincoln's
B. Both are secondary sources that summarize Lincoln and Douglas's important opinions.
C. Both could be used to support a historical argument about the Lincoln-Douglas debates.
D. Both are valuable to a historian as well-written primary source documents.