There are no mosquitoes in Iceland.
Why it is true
The rapid and drastic temperature changes in winter and the chemical composition of Icelandic water and soil make the environment inhospitable for the life cycle of these insects.
Source: Nordic Ecology
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.