The most relevant response for explaining the effect of dramatic irony in the passage would be:
Eve knows that the box does not contain a canteen, but Nikka does not realize it, which creates humor.
This response highlights the core of dramatic irony: the audience or reader has knowledge that a character does not, which creates a humorous tension in the scene. This understanding allows readers to appreciate the humor in the situation, as they anticipate Nikka's reaction when she discovers the true contents of the box, contrasting with her expectations.