Part A- The correct answer is C. Lincoln's use of the words anxiously, dreaded, and destroy give the paragraph an intense and foreboding tone.
Lincoln uses these words to give his speech a tone of reproach to the attitudes of those who, as he mentions, sought to unleash war. He speaks from a conciliatory position, but emphasizing that there were people who sought to harm the nation.
Part B- The tone identified in Part A and Lincoln's repeated use of the word all advance his purpose of explaining the broadly held view of war as a serious event that could easily have been avoided, if both the fear and the desire to avoid the conflict had prevailed over the interests that caused the Civil War to break out.