Answer:
B. They form cell membranes
Explanation:
There's not really an explanation, that's just a fact. A phospholipid bilayer has two layers of, yep, phospholipids. They stay together well and kind of move around a little, allowing small particles to pass through. There are some proteins in them also that help them function as cell membranes.
The Chinese, The Soviet Union, and North Korea
The Battle of Britain was the turning point.