Which of These Is a General Feature of the Lipid

Which of these is a general feature of the lipid bilayer in all biological membranes?

A) Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.
B) Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.
C) Polar,but uncharged,compounds readily diffuse across the bilayer.
D) The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.
E) The polar head groups face inward toward the inside of the bilayer.