The correct option is D Fibrous proteins are insoluble in water.
Polypeptide chain which is held together by disulphide or hydrogen bonds, tend to form fibre-like structure. These proteins are called fibrous proteins. These kind of proteins are insoluble in water. Examples for fibrous protein are keratins (present in hair,wool), elastin, fibroin (silk worms, spider silk and etc), myosin(present in muscles), etc,.