The naked mole rat feels no pain at all.
Why it is true
The naked mole rat is insensitive to a specific form of pain caused by acids, because it lacks the receptors responsible for that signal. However, it still feels other forms of pain, such as thermal and mechanical, making it a unique model for study.
Source: Science
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.