Helium escapes Earth's gravity into space.
Why it is true
Helium atoms are so incredibly light and unreactive that when released into the atmosphere, they eventually float up and drift away into outer space forever.
Source: Physics
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.