The correct option is
A crunch
An onomatopoeia is 'the formation of a word from the sound associated with what it's named'.Option A: 'Crunch' imitates the sound of the action 'crunch': to make a loud, muffled, grinding sound as if something brittle has been crushed.
It is relevant to 'leaves'. When leaves are dry, they make a 'crunching sound when the leaves ruffle'.
Hence, this option states the correct onomatopoeic word and option A is correct.
Option B: 'Crisp' means 'firm, dry and brittle'. It usually refers to food, like chips, and not to leaves. It and does not imitate its sound.
Option C: 'Woof' is the sound heard when a dog barks.
It is onomatopoeic but it does not resonate with the sound of leaves.
Option D: 'Yelp' means 'a short, sharp cry, especially of pain or alarm'.
It expresses the sound of the short sharp cry but it does not do so for leaves.
Hence, options B, C and D are wrong.