Final answer:
Lincoln feared that political division, largely driven by the issue of slavery, posed a significant threat to the unity and stability of the United States.
Step-by-step explanation:
Abraham Lincoln's fear for the United States, based on the sources provided, can be best described as a fear that political division will harm the United States. In his first inaugural address, Lincoln emphasized the permanent nature of the Union, which was threatened by the secession crisis and the deepening national division over slavery. Political division, which had been intensifying due to the slavery debate and subsequent events such as the Dred Scott decision, John Brown's raid on Harper's Ferry, and the splintering of the Democratic Party, was recognized as a key issue that could lead to the dissolution of the Union.
Lincoln's presidency, which was seen by the South as a direct threat to the institution of slavery upon which their economy and way of life were built, precipitated the secession of Southern states. Accordingly, the most appropriate statement that describes Lincoln's fear is: C. Lincoln fears that political division will harm the United States.