题干

蹦床比赛已被列入奥运会正式比赛项目,图是小朋友玩蹦床的情景,对他们在上升和下落过程中机械能的变化,下列分析错误的是(忽略空气阻力)(   )

A:小孩上升到最高点时的重力势能最大

B:小孩在空中下落的过程中重力势能转化为动能

C:小孩下落到最低点时的动能最大

D:小孩下落到最低点时蹦床的弹性势能最大

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C

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    Speaking in public is most people's least favorite thing. The reason is that we are all afraid of making fools of ourselves.____

    But stop biting your finger-nails. Public speaking is easy. It's just plain talking, and you talk all the time. Although I'm basically shy (honest!), I've been making speeches and talking on radio and television for more than 30 years, and I can tell you that public speaking is not a “gift” like musical talent.____ Here are some of the lessons I have learned:

    Your audience is going to come away with one or two of your main ideas. One or two. Not ten or 20.____ And if you don't have a clear idea of what you want to say, there's no way your audience will.____— how you are going to open, what major points you want to make and how you're going to close.

    When I do a radio or TV piece, I often write the last sentence first.____ A strong close is critical: the last thing you say is what your audience will most likely remember.

    The standard length of a vaudeville (杂耍) act is usually 12 minutes. If all those performers singing and dancing their hearts out couldn't go on longer without boring the audience, what makes you think you can?

A. Some people are born to be good at making speeches.

B. Anybody who can talk can speak in public.

C. Try to relax yourself before making the speech.

D. The more important the speech is, the more frightened we become.

E. If you can't express in a sentence or two what you intend to get across, then your speech is not focused well enough.

F. When you know where you're headed, you can choose any route to get there.

G. No matter how long or short your speech is, you've got to get your ducks in a row.