Answer: a. a tropical disease caused by a parasite
Malaria is a parasitic infection in humans caused by the parasite of the genus Plasmodium. The parasite is being transmitted to the human body by the bite of the Anopheles mosquitoes. The parasite multiply inside the red blood cells. Malaria occurs in the temperate regions, but commonly occur in the tropical and subtropics. It is related to cause attacks of fever, anemia and other fatal complications.