Answer:
B. The brutality of war.
Step-by-step explanation:
A theme is the lesson, or any moral or universal idea or message that is delivered or dealt in the story. The theme is the main idea that the story is about, the underlying meaning of that literary work.
Based on the options provided in the question, option B can be the only example of a literary theme. This theme of the brutality of war can be the theme of any story that is told, while the other options can be the basis of the story. They can be the background of the story but not the actual theme.