Answer: The repetition intensifies the speaker's sense of urgency.
Step-by-step explanation:
Repetition simply refers to a literary device that has to do with the intentional act of using a word for effect multiple times in a written work or speech.
The repetition of the word "must" affect the tone of the piece as it intensifies the speaker's sense of urgency. In this case, the use of must shows how important the situation is.