Which of the following pathogenic organisms is multicellular and includes tapeworms, roundworms, and flatworms?

Fungi are primarily unicellular or multicellular organisms that obtain nutrients through absorption. They include yeasts, molds, and mushrooms, but do not include helminths. Fungi are fundamentally different from helminths, as they are not classified as worms and do not possess the same biological structure or life cycle.

Protozoa are single-celled organisms that can be free-living or parasitic. They differ from helminths in size, complexity, and structure, as protozoa are microscopic and do not include multicellular organisms like tapeworms or roundworms. Therefore, they do not fit the description provided in the question.

Vectors are organisms, often arthropods like mosquitoes or ticks, that transmit pathogens from one host to another. They are not pathogens themselves and do not include any multicellular organisms, such as helminths. Thus, vectors do not align with the characteristics outlined in the question.