Explanation:
Issun Sengeki... Messatsu!
Alike of what the other guy said, only the female mosquito sucks blood.
Being that this is true, the mosquito(s) could have been in any environment. They could carry diseases and illnesses. On top of that, they can carry microscopic organism, unlike diseases, that can cause infections.
I would also say that the answer is C
The answer to this question would be: The soil
There are lots:
Biology and Medicine - cloning and expression of human insulin in bacteria (stopped having to produce it from pig pancreases); Watson & Crick discovery of the structure of DNA; gene therapy in humans
Chemistry - determination of the exact number of molecules in a mole (Avagadro's number); discovery of radioactivity (Rutherford); the invention of nylon (DuPont); Boyle's law (behavior of gases)
