African Trypanosomiasis, also known as “sleeping sickness”, is caused by microscopic parasites of the species Trypanosoma brucei. It is transmitted by the tsetse fly (Glossina species), which is found only in sub-Saharan Africa.

Answer:
The correct answer is A:
Explanation:
Sleeping sickness, also known as African trypanosomiasis, is caused by a protozoan called Trypanosoma. Here is a detailed explanation:
1. Sleeping Sickness:
- Sleeping sickness is a disease caused by infection with the protozoan parasite Trypanosoma brucei.
- It is transmitted to humans through the bite of infected tsetse flies, which are found in sub-Saharan Africa.
2. Protozoan:
- Protozoa are single-celled microscopic organisms that can cause various diseases in humans and animals.
- Trypanosoma is a genus of protozoa that includes several species responsible for causing different diseases in humans, including sleeping sickness.
3. Trypanosoma:
- Trypanosoma is a flagellated protozoan parasite.
- It has a complex life cycle involving both humans and tsetse flies.
- The parasite exists in two forms: a bloodstream form (found in humans) and a procyclic form (found in tsetse flies).
4. Sleeping Sickness Transmission:
- Tsetse flies become infected with Trypanosoma when they feed on the blood of an infected human or animal.
- The infected flies then transmit the parasite to humans through their bite.
- Once inside the human body, the parasite multiplies and spreads through the bloodstream, causing various symptoms.
In conclusion, sleeping sickness is caused by the protozoan parasite Trypanosoma, making option A the correct answer.