A policeman detained four suspects for a theft case. Alex: Hey, I didn’t do it! Ben: Alex did it. Clara: I did not do it! Denis: Ben did it.
Only one suspect told the truth. Who was the thief?
See the answer
Answer: Clara. Since only one suspect told the truth, the thief is either Alex or Clara. If Alex was the thief, then both Ben and Clara would have told the truth. So, Alex is not a thief. Therefore, it must be Clara.