27. There are three proteins X, Y, and Z in 20 mM Tris (pH 7.0) solution. 1. Protein X is a homoheptamer. Its pI is 9.2. The molecular mass of each subunit of theprotein X is 20,000 Da and the subunit's pl is 9.2.  2. Protein Y is a monomeric protein with molecular mass of 93,000 Da and its pl is 4.  3. Protein Z is a homodimer. Its molecular mass is 1 40,000 Da and its pI is 8. Please choose the correct answer?
(A) When this mixture is loaded onto a cation exchange column, only protein Y can bind to the column:
(B) When this mixture is loaded onto a size exclusion column, Protein Y is last eluted.
(C) When this mixture is analyzed by a SDS- PAGE, the lowest band is protein Y.
(D) When this mixture is analyzed by a SDS- PAGE, protein X and 'Z cannot be separated.
(E) When this mixture is loaded onto a cation exchange column, protein X is the first eluted protein.