The longest mountain range in the world is found at the bottom of the ocean.
Why it is true
The Mid-Ocean Ridge is over sixty-five thousand kilometres long and crosses all the major oceans.
Source: Oceanography Dept
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.