The driest desert in the world is in South America.
Why it is true
The Atacama Desert in Chile is the driest non-polar place on Earth. In some areas, it has never rained since records began, and humidity is almost non-existent.
Source: Geography
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.