Answer:
Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ). Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane.
They both involve topics related to the natural world, and are both based on empirical evidence. <span />
The right answer is <span>A) semi-permeable membrane
<span>A semi-permeable membrane is a membrane permeable to a liquid (solvent) and impermeable (or poorly permeable) to substances dissolved in the liquid (solute).
</span>The tubule of a kidney consists of a semi-permeable membrane and has also specific transporters which allow absorption and reabsorption. These "tools" allows some substances like ions to be absorbed/reabsorbed (by the transporters), without any changes in the concentration of the other substances (because both the membrane and the transporters stopped them).</span>
