Question

what is the main function of the cell membrane in a plant cell?
to give strength and stiffness to the cell
to control which substances enter and leave the cell
to use energy from sunlight to make sugar
to break down sugar and release energy that the cell can use

Explanation:

The cell - membrane is a selectively permeable barrier. Its main role is to regulate the movement of substances in and out of the cell, maintaining the cell's internal environment. Giving strength and stiffness is a function of the cell - wall in plant cells. Using sunlight to make sugar is photosynthesis in chloroplasts, and breaking down sugar for energy is cellular respiration in mitochondria.

Answer:

to control which substances enter and leave the cell