英语笑话:I can go home 我可以回家了

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（涂抹） . 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."