Which statement about the cell membrane is true? A) It contains cellulose and sugars that are involved in communication.

B) It is present in animal cells only.

C) It is rigid and elastic for supporting the cell's shape.

D) It prevents harmful substances from entering a cell.

Its D, The cell membrane(also known a the plasma membrane) has a job in which it has to allow passage in and out of the cell. Therefore it can prevent harmful substances from entering the cell. Think of it as security, either allowing you access or denying you depending on if you're a threat

D) it prevents harmful substances from entering a cell

Explanation:

The entire purpose of the cells membrane is to contain its organelles, the structures within it and prevent them from getting harmed by outside material.

i think the answer is b.

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.