Human stomach acid can dissolve razor blades.
Why it is true
With a pH between one and two, gastric hydrochloric acid is corrosive enough to break down metals like zinc and steel blades within hours.
Source: Scientific American
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.