Concept:Trypanosoma is a protozoan parasite that causes African trypanosomiasis.Explanation:Sleeping sickness, also known as human African trypanosomiasis, is caused by Trypanosoma brucei.It is transmitted by the tsetse fly in tropical Africa.River blindness is caused by a worm, yellow fever by a virus, and malaria by Plasmodium.Answer:A. sleeping sickness