Final answer:
The cell membrane is best described as being primarily responsible for maintaining cellular integrity due to its selectively permeable barrier formed by a phospholipid bilayer, embedded proteins, and cholesterol.
Step-by-step explanation:
The statement that best describes the cell membrane is b. The cell membrane is primarily responsible for maintaining cellular integrity. The cell membrane's essential function is to serve as a barrier, separating the cell's interior from the extracellular environment. The structure of the cell membrane is a phospholipid bilayer, which is both pliable and embedded with various proteins that perform different functions, such as transporters and recognition sites. Cholesterol within the membrane contributes to its fluidity and flexibility, particularly in response to temperature changes. The cell membrane is selectively permeable, regulating the entry and exit of substances, contributing significantly to the cell's homeostasis and overall integrity.