Which of the Following Is a Principle of the Fluid

Which of the following is a principle of the fluid mosaic model of cell membrane structure?

A) All proteins associated with the cell membrane are contained in a fluid layer on the outside of the cell.
B) Phospholipids consist of a polar head and a nonpolar tail made of three fatty acid chains.
C) The lipid bilayer is a solid at body temperature, thus protecting the cell.
D) Phospholipids form a bilayer that is largely impermeable to water- soluble molecules.