Cell Membrane Regulates Substance Entry

Steps:

• Identify the structure surrounding the cell's contents in the diagram.
• Recall that plant cells have a cell wall outside the membrane, but entry control is internal.
• Match labels to known organelles: membrane encircles cytoplasm.
• Confirm the part acting as a selective barrier for substances.

Why C is correct:

• The cell membrane (plasma membrane) is a semi-permeable phospholipid bilayer that controls substance entry via diffusion, active transport, and osmosis, per the fluid mosaic model.

Why the others are wrong:

• A: Cell wall provides structural support but is freely permeable and does not control entry.
• B: Cytoplasm is the fluid medium inside but does not regulate entry.
• D: Nucleus manages genetic information but is internal and unrelated to external entry.

Final answer: C