This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Most common protozoan parasite is 
Select and explain. 
A. Toxoplasma gondii, B. Trypanosoma, C. Plasmodium, D. All of the above
A: Toxoplasma gondii
Answer: A: Toxoplasma gondii 
Explanation: Toxoplasma gondii is an obligate intracellular parasitic one-celled eukaryote  that causes the infectious disease toxoplasmosis  domestic cats, are the only known definitive hosts in which the parasite may undergo sexual reproduction.
In humans, T. gondii is one of the most common parasites in developed countries.