According to the Fluid Mosaic Model of Cell Membranes, the Fluid

According to the fluid mosaic model of cell membranes, the fluid part of the model refers to ____.

A) the constant movement of the hydrophilic tails in the interior of the membrane
B) a thin layer of water found sandwiched between the two layers of phospholipids
C) the phospholipid molecules that vibrate, spin, and exchange places within the same layer of the bilayer
D) the free movement of cholesterol molecules within the membrane
E) the frequent flip-flop of phospholipids from one side of the membrane to the other