Concept:The contractile vacuole is an organelle found in Protozoa for osmoregulation.Explanation:I. Stomata are found in higher plants, not in Spirogyra (an alga).II. Alveoli are respiratory structures in mammals, not in earthworms.III. Malpighian tubules are excretory organs in insects, not in mammals.IV. Protozoa such as Amoeba and Paramecium use the contractile vacuole to remove excess water.Answer:D. IV