题目

If you go to a supermarket and find that there ________ cashier(收银员), would you still pay for your things? People in our ________ are having a test of honesty(诚信测试) now. The supermarket here ________ a special area. This area sells ________ things like pens and knives. People need to scan(扫描)their things, and put the ________ into the cash desk all by themselves. ________ watches them. By now, the supermarket runs very ________. People say they enjoy the feeling of ________ honest.Once I go to the supermarket to ________ a note book. When I am ready to pay, I find I have no _如图所示，两个半径相同的半圆形光滑轨道置于竖直平面内，左右两端等高，分别处于沿水平方向的匀强磁场和匀强电场中．两个相同的带正电小球同时从两轨道左端最高点由静止释放．M、N为轨道最低点，则下列说法中正确的是（　　）A．两个小球到达轨道最低点的速度vM＞vNB．两个小球第一次经过轨道最低点时对轨道的压力FM＞FNC．小球第一次到达M点的时间大于小球第一次到达N点的时间D．磁场中小球能到达轨道另一端最高处，在电场中小球不能到达轨道另一端最高处