题干

如图所示,平行板电容器中悬浮一个带电微粒P,今把A、B两个半方形金属盒相对插入电容器两板间,当A、B合拢时,对微粒运动情况的判断正确的是(   )

A:向上运动

B:向下运动

C:仍保持静止

D:条件不足,无法判断

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答案(点此获取答案解析)

B

同类题1

阅读理解七选五。根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Public Speaking Training

·Get a coach

    ____,so get help. Since there are about a billion companies out there all ready to offer you public speaking training and courses, here are some things to look for when deciding the training that's right for you.

·Focus on positives

    Any training you do to become more effective at public speaking should always focus on the positive aspects of what you already do well. Nothing can hurt confidence more than being told that you aren't doing well. ____, so good public speaking training should develop those instead of telling you what you shouldn't do.

·____    If you find a public speaking course that looks as though it's going to give you lots of dos and don'ts, walk away! Your brain is so full of what you're going to be talking about.

    ____ As far as we're concerned, there are basically no hard and fast rules about public speaking. Your audience can be your friends.

·You are a special person not a clone

    Most importantly, good public speaking training should treat you as a special one, with your own personal habits. ____ Your training course should help you bring out your personality, not try to turn you into someone you're not.

A. You aren't like anybody else

B. You already do lots of things well

C. Turn your back on too many rules

D. Check the rules about dos and don'ts

E. Whatever the presentation, public speaking is tough

F.The one thing you don't want is for them to fall asleep

G. So trying to force a whole set of rules into it will just make things worse