According to widely accepted "Fluid mosaic model" cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statements is incorrect [CBSE PMT 2005]

• A. Proteins in cell membranes can travel with in the lipid bilayer
• B. Proteins can also undergo flip-flap movements in the lipid bilayer
• C. Proteins can remain confined within certain domains of the membrane
• D. Many proteins remain completely embedded within the lipid bilayer