There was a college professor teaching on the study of birds. After the class one day he told his students there would be a test on Monday and that they should study over the weekend. Since the professor was known for hard tests, they all went home and crammed and crammed and studied till their heads hurt. Finally the weekend was over and they found themselves back in class waiting to take a test.

The professor came in and with him he brought five bird cages each covered with a blanket. He told everyone to get out paper and something to write with. He then began to uncover each one but he stopped when only the bird's legs were showing. "Identify each bird by their legs." he said. Each student gasped, they didn't know what to do. How could they identify a bird by its legs they all look the same. Some sat there and frantically tried to guess.

Finally after they had been trying to guess for a while, a brave student stood up. "Professor this is impossible how do you expect us to tell what a bird is by its feet? They all look the same."

With that the student started to walk out of the room but before he could make it, the professor said, "Wait a minute! Who are you?"

The student looked at him lifted his pant leg and said, "YOU TELL ME."