B. It helps to narrow the topic.
Answer:
c) poison gas
Explanation:
War-weary troops are gassed in Wilfred Owen's "Dulce Et Decorum Est," and the "helpless" speaker watches as one of them "chokes" and "drowns" in the fumes because he is unable to get to his mask in time.
The story is in the screenshot, I hope it helps you :)
It'd be a metaphor. A metaphor is a figure of speech where an object or phrase is applied to an object or action where it isn't literally applicable.