A cell membrane is surrounded by fluid. A cell membrane is semipermeable. A cell membrane holds organelles in place. A cell membrane is found in plant and animal cells.
I gave my students this multiple choice question: Which characteristic of a cell membrane allows it to control materials entering and leaving a cell?

Only one answer is correct among these 4 choices:
- A cell membrane is surrounded by fluid.
- A cell membrane is semipermeable.
- A cell membrane holds organelles in place.
- A cell membrane is found in plant and animal cells.

Could you tell me which one is correct?

A cell membrane is semipermeable.