Explanation:

- Option:1, Bacteria

- Bacteria are single-celled microorganisms, some of which cause diseases like tuberculosis and strep throat. However, they do not cause Ebola.

- Option:2, Fungus

- Fungi are a separate kingdom of organisms, which include yeasts and molds. They can cause infections like athlete's foot but are not responsible for Ebola.

- Option:3, Virus

- Viruses are tiny infectious agents that replicate only inside living cells. The Ebola virus is indeed a virus and is the causative agent of the Ebola disease.

- Option:4, Protozoan

- Protozoans are single-celled eukaryotes that can cause diseases like malaria. They do not cause Ebola.