Which statement most completely describes the role of the cell in a single-celled organism?
it provides the chemical functioning and genetic material that enables life, growth, and reproduction.
it provides the organism with nutrition and a means of locomotion.
it provides a boundary between the organism and its environment.
it provides the support structure that the organism lacks because it has no true skeleton.

Juan and carol were studying invertebrates in biology. they knew that segmented or earth worms preferred a dark, moist habitat. during this lab, they would be investigating the responses of organisms called planaria or dugesia tigrina. these were simple flatworms that still had a one-way digestive system and a very simple nervous system. juan and carol placed the planaria in a petri dish containing cool, distilled water that was partially covered with black paper. they shined a light on the dish. next, they removed the paper and placed a small amount of chicken liver at one end of the dish. they added a few large salt crystals to the water. finally, they added drops of hot water to the cool water in the petri dish. their results can be seen in the data table. according to their experiment, all but one conclusion is valid.