The correct answer is - C. tropical.
The tropical regions near the Equator are a fertile soil for the development and spreading of lots of dangerous diseases, mostly being transferred to the humans by some of the insects.
The malaria is in fact a disease that is transferred to the humans by an insect bit, more specifically, by the bite of the Anopheles mosquito. If the mosquito is infected with the Plasmodium parasite, it carries it around with it in its body, and when the infected mosquito bites a human, than the mosquito is released to the bloodstream of the victim, and causing malaria.
