Napoleon was ill     

    Jack had gone to the university to study history, but at the end of his first year, his history professor failed him in his exams, and he was told that he would have to leave the university. However, his father decided that he would go to see the professor to persuade him to let Jack continue his studies.

    "He's a good boy," said Jack's father, "and if you let him pass this time, I'm sure he'll improve a lot next year and pass the exams at the end of it really well."

    "No, no, that's quite impossible," replied the professor immediately. "Do you know, last month I asked him when Napoleon had died, he didn't know!"

    "Please, sir, give him another chance," said Jack's father. "You see, I'm afraid we don't take any newspaper in our house, so none of us really know that Napoleon was ill."   

    What's the use of it

    A: "What's the purpose of the propeller?"

    B: "To keep the pilot cool. If you don't think so, just stop it and watch him sweat!"