这篇阅读理解我看太懂，请老师指点指点：

   It doesn't make any difference how long your speech is.Unless you tune in the first 60 seconds,the chances are they will tune you out.

   Take the fellow who opens:"On my way over to the club tonight,i ran into a bum who asked me for $49.50 for a cup of coffee.I told him he'd do much better if he asked for a quarter."He said,"Do you think i'm going into the Ritz in these clothes?"We know his purpose:to win his audience over with humor,however,has no connection with his speech.He has his audience laughing at he wrong time.Once you have an audience laughing it's hard to get them to switch to an entirely different train of thought.There is nothing wrong with humor in a speech as long as it has something to do with the purpose of his speech.To open a speech with humor just to be entertaining invites an almost sure "turnoff" for the rminder of the talk.