What Is the Principle of Polyacrylamide Gel Electrophoresis (PAGE)

What is the principle of polyacrylamide gel electrophoresis (PAGE) ?

A) Porous gel retards the movement of small molecules.
B) The negative charge of detergent overpowers the charge of the protein, and separation of molecules occurs by ion exchange.
C) Porous gel allows small molecules to move freely and retards the movement of larger molecules.
D) Support media contains antibodies that will bind specific proteins, and those not bound are washed away.