(a) perichondrium

Explanation:

Cartilage is a type of connective tissue consisting of cells (called chondrocytes) and though flexible matrix made of collagen, protein, and sugar. The cartilage is covered on the outside by death of white fibrous connective tissue called perichondrium. Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. It contains the blood vessels and nerves that provide nourishment and sensation.

Endosternum is a collective name for the apodemes or interior processes of the sternum in the thoracic of an insect. The peritoneum is thin membrane that lines the abdominal and pelvic cavities and covers most abdominal viscera.