One day after school the teacher said to his students, "Tomorrow morning, if any one of you can answer my first question, I will permit him or her to go home earlier."

The next day, when the teacher came into the classroom, he found the blackboard daubed（亂畫）. He was very angry and asked, "Who did it? Please stand up!"

"It's me," said Bob, "Now, I can go home. Good-bye, Sir."