Answer:
The audience knows the boastful king's power did not last.
Step-by-step explanation:
According to the poem, there is a narration of a king who boasts and terrifies people.
Therefore, the sentence that best describes the dramatic irony in the poem is that the audience knows the boastful king's power did not last.
Dramatic irony is a situation whereby the audience already knows the outcome of a scene or the entire play whereas the actor or dramatist is unaware.