Answer:
By starting each line with a type of worker, repeating the word "singing", and ending each line with what each person does while singing.
Step-by-step explanation:
Whitman uses repetition in this passage from his poem by:
starting each line with a type of worker (the carpenter, the mason, the boatman, the deckhand, the shoemaker, the hatter)
repeating the word "singing"
ending each line with what each person does while singing (measures his plank or beam, makes ready for work, or leaves off work, belongs to him in his boat, on the steamboat deck, sits on his bench, stands)
Therefore, the correct answer is: by starting each line with a type of worker, repeating the word "singing", and ending each line with what each person does while singing.