2. Please choose the correct answer from the following descriptions: 1. Dextran is homopolysaccharide and the material for beads in gel filtration. 2. Agarose is the material for making SDS gel. 3. Heparin is sulfated hetereopolysaccharide.  4. The strength of a-keratin depends on its Cys content. 5. Hydrogen bond in a-helix formed between residue i and i+4.
(A) I and 3 are incorrect.
(B) 2 and 5 are incorrect.
(C)2 and 5 are correct
(D) Only 2 is incorrect.
(E) Only 3, 4, and 5 are correct.