Which of the following is a characteristic of the plasma membrane? To protect the cell's internal contents, water is the only substance that can freely pass through the plasma membrane.

Only small molecules are allowed into and out of the cell by the plasma membrane.

Its selective permeability allows certain molecules, such as oxygen and carbon dioxide, to flow freely in and out of the cell while controlling the flow of other molecules.

The structure of the phospholipids forms a stiff protective outer shell around the cell's internal contents.