I believe the answer is b.
A phospholipid bilayer or lipid bilayer is a double layer of lipids in a cell membrane which has a hydrophobic and a hydrophilic part.
Hydrophobic - expelled by water
Hydrophilic - attracted to water
The layers form the cell membrane which means that it's functions are the same as the functions of a cell membrane, and are critic to the cells functioning.
Hope it helped,
BioTeacher101
In my opinion, the correct answer among the choice given above is option D. It is advantageous for grazing mammals to gather in groups because groups <span>offer greater protection from predation. It protects them because predators will think twice in nearing the group because it is outnumbered.</span>
As the phase changes occur, the freedom of motion of the particles increases.