C. Medusa. Everything else on the list is a part of another creature, medusa is the only cnidarian here!
The answer is oxygen end, because the oxygen atoms attract electrons more strong than hydrogen atoms, because of unequal sharing of electrons gives the water molecule a small negative (-) charge close to its oxygen atom
Gas exchange in humans is the delivery of oxygen lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs.
Its ethier loose soil or dense vegetation but i have a feeling its loose soil.
Selectivity permeable membrane and a scaffold for biochemical activity
