What does membrane mean when referring to a cell?

The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The cell membrane consists of a lipid bilayer that is semipermeable. The cell membrane regulates the transport of materials entering and exiting the cell.

Explanation:

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A qualitative observation is done by describing the quality of an object without the use of numbers. I think the correct answer from the choices listed above is option B. The color of flowers is compared is a qualitative observation.