Final answer:
Elodea is the multicellular organism among the given options. Although most protists are unicellular, Elodea is an exception as a multicellular aquatic plant.
Step-by-step explanation:
The question asks which one of the provided options is multicellular. Among the listed organisms, Elodea is a multicellular organism. Amoeba, trichonympha, and protococcus are all single-celled. To elaborate, amoebas and trichonympha are both types of protists, which are primarily unicellular eukaryotes, and protococcus is a single cell green algae. In contrast, Elodea is a type of aquatic plant and is made up of many cells, which demonstrates multicellularity.
While focusing on the broader context, it should be noted that most protists are unicellular, although there are exceptions, such as certain types of algae, like kelp. Protists can range from single-celled organisms like amoebas to multicellular organisms like seaweed. Multicellular protists like Elodea do not show the same level of cellular specialization as seen in multicellular plants, animals, or fungi.