Concept:Protozoans are single-celled organisms, whereas Ascaris is a multicellular parasitic worm.
Explanation:Protozoans are microscopic, unicellular organisms that carry out all life processes within one cell.
Amoeba, Plasmodium, and Paramecium each belong to this protozoan group.
Ascaris, however, is a parasitic roundworm classified under Nematoda.
It has a multicellular body with tissues and organ systems, unlike true protozoans.
Therefore, among the given organisms, Ascaris is not a protozoan.
Answer:B. Ascaris