Which of the following statement(s) is correct?

(A). Keratin is an example of fibrous protein.
(B). Fibrous proteins are water-soluble, while globular proteins are water-insoluble.
(C). Polypeptide chains in fibrous proteins run parallel and are held together by hydrogen and disulphide bonds.
(D). Insulin and albumins are common examples of globular proteins.

Choose the correct answer from the options given below:

(A), (C), and (D) only

The correct answer is Option (4) → (A), (C), and (D) only

(A) Keratin is an example of fibrous protein: CORRECT. Keratin is the structural protein found in hair, nails, and the outer layer of skin. It is a classic example of a fibrous protein.

(B) Fibrous proteins are water-soluble, while globular proteins are water-insoluble: INCORRECT. This statement is the reverse of the truth. Fibrous proteins (like keratin and collagen) are generally insoluble in water because of their long, rope-like structures. Globular proteins (like insulin and hemoglobin) are folded into spherical shapes with hydrophilic groups on the outside, making them soluble in water.

(C) Polypeptide chains in fibrous proteins run parallel and are held together by hydrogen and disulphide bonds: CORRECT. Fibrous proteins consist of polypeptide chains that run parallel to each other, forming fibers. These are stabilized by strong intermolecular forces like hydrogen bonds and disulfide linkages ($S-S$ bonds).

(D) Insulin and albumins are common examples of globular proteins: CORRECT. Insulin (a hormone) and albumins (found in egg whites or blood) fold into compact, rounded shapes, which is the defining characteristic of globular proteins.