What is the main function of the cell membrane of a cell?

A. to exchange nutrients and the cells waste with the external environment

B. to limit the size that cell can reach

C. To organize the cell's internal contents

D. to protect the cell from harmful substances in the environment

D. to protect the cell from harmful substances in the environment

Explanation:

Cell membrane is also known as plasma membrane is a biological membrane that differentiate the internal organelles of the cells from the outside environment. Cell membrane is made up of phospholipid bilayer with embedded proteins.

The main or primary function of cell membrane is to protect cell from harmful substances in the environment as it is the outer convering of the cell. cell membrane regulates movement of substances in and out of cells which restricts entry of harmful substances and hence called as selectively permeable membrane.

Hence, the correct option is D.