Which of the Following Statements Concerning the Plasma Membrane Is

Which of the following statements concerning the plasma membrane is correct?

A) Under a light microscope, the plasma membrane appears as a trilaminar structure.
B) The carbohydrates on the outer surface of the membrane serve as receptor sites for binding chemical messengers in the environment of the cell.
C) The lipid bilayer serves as a barrier to the passage of H₂O-soluble substances through the membrane.
D) Carrier proteins shuttle back and forth across the membrane as they carry passenger molecules from one side to the other.