The correct answer is: B. Parasite.
A symbiont is an organism that lives in a mutually beneficial relationship with another organism. A parasite is an organism that lives on or in another organism (its host) and benefits by deriving nutrients at the host’s expense. A saprophyte is an organism that obtains its nutrients from dead or decaying organic matter.
Plasmodium is a genus of parasitic protozoa that cause malaria in humans. The parasites are transmitted to humans through the bite of infected mosquitoes. Once inside the human body, the parasites multiply in the liver and then invade red blood cells. The destruction of red blood cells causes the symptoms of malaria, including fever, chills, and anemia.
Plasmodium is not a symbiont because it does not benefit its host. In fact, it causes the host to become ill. Plasmodium is also not a saprophyte because it does not obtain its nutrients from dead or decaying organic matter. Instead, it obtains its nutrients from living human cells. Therefore, the correct answer is B. Parasite.