Concept:Bone, an animal by-product, has many uses, but it is not used to make leather.
Explanation:The illustrated animal by-product is bone, which is obtained from slaughtered animals.
Bones can be processed into fertilizer, bone meal, and buttons.
Leather, however, is made from the hide or skin of animals, not from bones.
Therefore, bone is not used in the production of leather.
Answer:D. leather
