The correct answer is (d).
The plasma membrane is a thin, flexible barrier that surrounds all cells. It is made up of a phospholipid bilayer, which is a double layer of phospholipid molecules. Phospholipids are molecules that have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. The hydrophilic heads of the phospholipids face the inside and outside of the cell, while the hydrophobic tails face each other in the middle of the membrane.
The plasma membrane is also studded with proteins. These proteins serve a variety of functions, such as transporting molecules across the membrane, sensing changes in the environment, and attaching the cell to other cells.
Carbohydrates are not a major component of the plasma membrane, but they can be found attached to proteins and lipids. These carbohydrates help the cell to recognize other cells and to attach to surfaces.
In conclusion, the plasma membrane is made up of both proteins and lipids. These two components work together to form a barrier that protects the cell and allows it to communicate with its environment.