A positively charged ion is called cation.
A negatively charged ion is called anion.
A salt is formed by the ionic bonding of a cation and an anion.
pH is a measure of the hydrogen ion concentration in a solution.
The size of food web is limited by the number of animals included in the area.
-Pepetreefrogthe2nd
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>
