The correct answer is option 3, Keratin. Fibrous proteins are proteins that have a long, filamentous shape. They are made up of repeating structural units and are insoluble in water. Keratin is a fibrous protein that is found in structures such as hair, nails, and the outermost layer of the skin. It provides strength and structural support to these tissues.
Haemoglobin, option 1, is a globular protein that carries oxygen in the blood. It has a compact, spherical shape.
Albumin, option 2, is also a globular protein that is found in blood plasma. It helps regulate the osmotic pressure of the blood and transports various substances.
Enzymes, option 4, are globular proteins that catalyze chemical reactions in the body. They have specific 3D structures that allow them to bind to substrates and facilitate chemical reactions.
Therefore, the correct answer is option 3, Keratin.