The right answer is A) semi-permeable membrane
A semi-permeable membrane is a membrane permeable to a liquid (solvent) and impermeable (or poorly permeable) to substances dissolved in the liquid (solute).
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).