Unicellular and simple multicellular organisms isolate and eliminate waste materials by:
a. filtering the wastes into a collecting tubule and then selectively reabsorbing key solutes before excretion.
b. filtering the wastes through specialized filters in the plasma membrane and into the extracellular space.
c. secreting wastes into excretory tubules that connect to the outside of the cell.
d. moving the wastes into a contractile vacuole and eliminating them through exocytosis.
e. All of these choices are correct.

The correct option is d.

Unicellular and simple multicellular organisms isolate and eliminate waste materials by: moving the wastes into a contractile vacuole and eliminating them through exocytosis.

Explanation:

In all living systems, from prokaryotes to more complex multicellular eukaryotes, the regulation of substance exchange with the inanimate world occurs at the level of the individual cell and is performed by the cell membrane. The cell membrane regulates the passage of materials into and out of the cell, a function that makes it possible for the cell to maintain its structural and functional integrity. This regulation depends on interactions between the membrane and the materials that pass through it. Non-assimilable substances accumulate in vacuoles or fuse with the plasma membrane, and exocytosis expels their contents.

Exocytosis is an inverse process of endocytosis, in which an intracellular vesicle approaches the plasma membrane fusing with it so that the content of said vesicle is poured into the extracellular environment. By exocytosis, the cell can expel the remains of the cell digestion process that are not useful to it and also the secretion products from the Golgi apparatus in the form of secretory vesicles. If too much water enters the cell, it could dilute the cell contents to the point of interfering with biological functions and could eventually break the cell membrane. In the Paramecium, there is a specialized organelle, the contractile vacuole, which prevents this from happening since it collects water from various parts of the cell and pumps it out with rhythmic contractions.