Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals?

• A. Membrane proteins attach the membrane to the cytoskeleton.
• B. Membrane proteins possess enzymatic activity.
• C. Membrane proteins form channels, which move substances across the membrane.
• D. All of the listed responses are correct.
• E. Membrane proteins with short sugar chains form identification tags that are recognized by other cells.