Concept:Polio is an infectious disease caused by a specific type of pathogen that attacks the nervous system.
Explanation:Polio, also known as poliomyelitis, is caused by the poliovirus. This pathogen is a virus, not a protozoan, bacterium, or fungus. The poliovirus is highly contagious and spreads through contaminated food, water, or direct contact with an infected person. Once inside the body, it destroys nerve cells, leading to paralysis or even death. The first effective vaccine for polio was developed by Jonas Salk in 1955. Since polio is caused by a virus, it is classified as a viral disease. The other options—protozoa, bacteria, and fungi—cause different diseases (e.g., malaria, tuberculosis, ringworm), not polio.
Answer:B. Virus