In fibrous proteins, polypeptide chains are held together by ___________.

In fibrous proteins, polypeptide chains are held together by disulphide and hydrogen bond in a parallel manner, due to which fibrous like structure is obtained. So options (ii) and (iv) are correct.

Vander Waals forces and electrostatic forces of attraction are not present in the fibrous protein. Therefore, (i) and (iii) are wrong.