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
In SDS-PAGE (Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis) proteins are separated on basis ofa) Massb) Chargec) Densityd) Molecular weighte) Solubility 
Select and explain. 
A. b, B. ad, C. ac, D. ab
B: ad
Answer: B: ad 
Explanation: In SDS-PAGE the separation of molecules depends mainly on their molecular size.
Therefore, SDS-PAGE is commonly used for molecular weight determination.