Read these sentences from paragraph 3.
These slaves constituted a peculiar and powerful interest. All knew that this interest was somehow the cause of the war. To strengthen, perpetuate, and extend this interest was the object
for which the insurgents would rend the Union even by war,while the Government claimed no right to do more than torestrict the territorial enlargement of it.

What does Lincoln use the word interest to describe?

A. the shared goals of those who supported slavery
B. the cost in money and Iives of pursuing the war
C. the focus of the nation upon the issue of slavery
D. the struggle of the enslaved population for freedom