Final answer:
Lincoln's opening sentence in the Gettysburg Address underscores the Civil War as a test of the nation's commitment to the principles of liberty and equality, suggesting the war is in defense of the nation's founding values. Therefore, the correct option is B.
Step-by-step explanation:
The opening sentence of Lincoln's Gettysburg Address, "Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal," strongly portrays the Civil War as a continuation of the United States' enduring commitment to liberty and equality. The effect of this opening on Lincoln's message is that it connects the sacrifices made during the Civil War to the ideals established at the founding of the nation, emphasizing that the present conflict was a test to see if a nation conceived on such principles could endure. This infers that the answer to the student's question is option (b), which aligns with Lincoln's emphasis on the permanent nature of the Union and its foundational ideals in his speeches and addresses during the Civil War.