Concept:Sleeping sickness is a parasitic disease caused by protozoa of the genus Trypanosoma.Explanation:The causative agent is Trypanosoma brucei, transmitted by the tsetse fly (Glossina species).It is prevalent in sub-Saharan Africa.The parasite invades the central nervous system, leading to sleep disturbances and other neurological symptoms.Other options: Leishmania causes leishmaniasis, Plasmodium causes malaria, and Paramecium is a free-living ciliate, not pathogenic.Answer:Option A: Trypanosoma.