Lincoln joined a volunteer company in the Black Hawk War in 1832. He served only three months in the war, and he never saw battle. Even so, Lincoln considered this event to be one of the greatest successes of his life. The men in his company elected him captain, and Lincoln was very proud of, yet humbled by, their confidence in him. How does this source add to the reader's understanding of Lincoln? It shows that he was frightened by battles and war. It shows that he took his leadership roles seriously. It shows that he had only a few successes in his life. It shows that he had too much confidence in himself.

This source adds to the reader's understanding of Lincoln in the sense that:

B. It shows that he took his leadership roles seriously.

Explanation:

According to the passage, one of the reasons why Lincoln considered his time in the war successful was the fact that he was elected captain by the men in his company. That already shows Lincoln values his role as a leader. But the passage also makes a point of mentioning that he was "very proud of, yet humbled by, their confidence in him." This information lets us know that he was not an overly confident men. Maybe he wouldn't have volunteered himself to become a captain but, since the men trusted him, he was happy to do it. With that in mind, we can choose letter B as the best option:

B. It shows that he took his leadership roles seriously.