oh i get it...thankyou very muchA primary structure of a protein is held by peptide bonds only. So there are no hydrostatic forces of attraction at all. This makes option A wrong.
There are no ionic bonds in a secondary structure, only hydrogen bonds (responsible for the alpha-helix and beta-plated sheet). This makes option B wrong.
Everything is correct with option C.
There are definitely hydrogen bonds holding a quaternary structure together. There are also no peptide bonds linking two different polypeptide chains.
One more point I'd like to clarify, When I say that a quaternary structure doesn't have any peptide bonds, I don't mean that there are no peptide bonds at all. All I'm saying is that it's not responsible for forming and maintaining a quaternary structure.