Silk Contains Many Pleated Sheets, Which Consist Predominately of Amino

Silk contains many pleated sheets, which consist predominately of amino acids such as phenylalanine and valine. Silk is more waterproof than cotton. Why?

A) Pleated sheet structure of silk occurs when mostly nonpolar amino acids are grouped together.
B) Pleated sheet structure of cotton occurs when mostly polar amino acids are grouped together.
C) It is the secondary, tertiary and quaternary structure of silk that make it repel water.
D) Since cotton is made from a plant, it cannot have nonpolar molecules.