(b) collagen

Explanation:

Collagen is the major protein of connective tissue. Collagen, in the form of elongated fibrils is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea cartilage, bone , blood vessels, the gut, and intervertebral disc. Collagen performs a very important role in ageing processes.

Myosin, commonest protein in muscle cells, is responsible for the elastic and contractile properties of muscle. It combines with actin to form actomyosin. Melanin is a black or dark brown pigment that is responsible for the dark colour of the skin, hair, scales, feathers and eyes of animals. Keratin is a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair, feathers, nails and hooves.