This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Protein separation based on moleular size ? 
Select and explain. 
A. HPLC, B. Gel filtration chromatography, C. Salting out, D. Affinity chromatography
B: Gel filtration chromatography
Answer: B: Gel filtration chromatography 
Explanation: Protein solubility Salting out' or salt extraction (precipitation of protein by ammonium sulfate)Molecular size * Gel filtration chromatography (molecular-sieve chromatography or size exdu- sion chromatography)UltracentrifugationSDS-PAGE (Sodium dodecyl sulphate-polyacrylamide gel electrophoresis)DialysisMolecular charge (Ionic charge) * Ion exchange chromatographyHigh performance liquid chromatography (HPLC)Electrophoresis (simple on cellulose acetate starch gel)lsoelectric focusing (a variant of electrophoresis)Molecular charge and molecular weight PAGE : polyacrylamide gel electrophoresisAffinity binding Affinity chromatographyHydrophobicity Hydrophobic interaction chromatography