The plasma membrane is a bilayer. lipid phospholipid carbohydrate protein

Option B. "Phospholipid"

Explanation:

Plasma membrane is a biological membrane that covers the outermost layer of the organism. It's composition varies in some of bacterial cells but most of them are made up of phospholipid bilayer.

Phoshpolipid bilayer are amphiphilic in nature with two hydrophobic fatty acid tails and one hydrophilic phosphate head.

It's main function is it acts a barrier to keep the proteins other molecules and ions out of the cell and diffuses them across this membrane when it is require.

Thus, the correct answer is phospholipid.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.