Cartilage is more difficult to heal than bone because cartilage:

Explanation

Cartilage is more difficult to heal than bone primarily because it lacks a vascular supply, meaning it has very limited blood flow. Vascular supply is crucial for the transportation of nutrients, immune cells, and growth factors needed for the healing process. Without a good blood supply, cartilage has a limited ability to repair itself compared to bone, which has a well-developed blood supply to support its healing and regeneration. The other options mentioned also play a role in cartilage's limited healing capacity. For instance, option B is partially true, as cartilage has fewer cells in its deeper layers, which can hinder the healing process. However, the lack of a vascular supply is the most significant factor contributing to the difficulty in cartilage healing.