Fingerprints form in the fetus before birth.
Why it is true
Fingerprints begin to form in the fetus around the 10th week of pregnancy and are fully formed by 4 months. They are unique to each person, even in identical twins.
Source: American Academy of Dermatology
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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.