Apples float in water.
Why it is true
About 25 percent of an apple's volume is air, which makes its density lower than that of water. That is why apples float. This air also helps the apple stay firm and crisp.
Source: USDA
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.