Definition of fallacy: A mistaken belief; misconception.
Definition of evasion: The action of avoidance;dodging.
Usually, sometimes in the introduction, they'll be avoidance of the actual point also known as evasion. But the question is asking to demonstrate the fallacy of evasion, basically asking to identify the misconception of the avoidance in the passage.
William Hammond seems to be the target point in the passage, talking about the accomplishment he made during The Civil war, so the parts in the passage that mentions what he did and why he did is "D. William Hammond, the surgeon general of the Union Army, created a new system of sanitary field care" and "E. It is probable that without Hammond's new system, more soldiers would have lost their lives." Eliminate these answers.
Answer F is after the introduction and after the point is stated, so that's not it. Eliminate F.
Between A, B, and C, A seems the most avoiding and farther from the point other than B and C that are more closer. My final answer would be A. The Civil War was the bloodiest conflict in the history of the United States.
Hope it helps and have a wonderful rest of your day/night!