我想在课前2分钟的英文演讲说一个笑话,说什么好呢

笑话都是三两句就说完的,1－2分钟什么都不好笑了.
two cows are talking on a farm.one said "now mad cow disease is everywhere,you better watch out." the other one respond "why,it won't effect us ducks."
two men are watching a burning hotel,one said to the other "i was lucky,all the people running out the hotel for their lives and no one had the chance to take their expensive things with them.and i was able to take them all".the other man looked at this guy and said,"do you know what my job is?" "no" "i'm a policeman",the man then said "and do you know what my job is" "no" "i'm a writer"...