29. A protein mixture contains proteins A, B, and C (Protein A: homodimer M. = 140,000, pI 8； Protein B:Mr = 113,000, pI 5； Protein C: Mr = 13,000, pI 9). 1. Sandy used SDS-PAGE to separate theses three proteins. The sequence of theprotein bands shown in gel from top to bottom is A-B-C. 2. Simon dissolved the protein mixture in 20 mM phosphate buffer (pH 7) andloaded to a cation exchange column equilibrated with the same buffer. ProteinB could not bind to the column.  3. Samuel dissolved the protein mixture in 20 mM phosphate bufter (pH 7) andloaded to an anion exchange column equilibrated with the same buffer. Onlyprotein A and C could bind to the column. 4. Silvia used a gel filtration column to separate them, C will be eluted first.  5. Sophie used 2-Dimensional electrophoresis to separate them. The relativepositions of these three proteins is like the image below.
  

(A) 1, 2, and 5 are correct.
(B) 2 and 4 are incorrect. 
(C) 1, 3, and 4 are incorrect.
(D) Only 2 is correct.  
(E) Only land 3 are incorrect.