There is a lot of systems what r u asking about
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 answer is #2 because it was a steady growth but when 1910 came it started to fluctuate.
The Caddoes, The Coahuiltecans, The Karankawas, The Wichitas thats all i know.