We can observe the use of alliteration and onomatopoeia in the options. Alliteration is the repetition of the sounds and onomatopoeia is a word or phrase that imitates the sound. We cannot observe the latter in the excerpt. But we can certainly observe alliteration in the repetition of the sounds b and p:
before us, mottled bodies, eyes black ice
bright as painted ponies, the babes brown-striped, not black
Additionally, the author uses a playful mood, not the angry one because of the description of the animals. We don't observe the angry nature of hyenas or zebras. Therefore, the correct answer is the third one - The author uses alliteration to create a playful mood.
