Question
Leaving a restaurant, a diner takes a black umbrella from the stand by the door, genuinely but mistakenly believing it to be the one she arrived with. Her own umbrella is identical in appearance. The umbrella she takes belongs to another diner. She discovers the mistake when she gets home and decides to keep it because 'they are all the same anyway'.
Suggested time: about 2 minutes. Choose the single best answer, then read why each option is right or wrong.