题目

如图所示，水平放置的光滑金属长导轨MM′和NN′之间接有电阻R，导轨平面在直线OO′左、右两侧的区域分别处在方向相反与轨道平面垂直的匀强磁场中，设左、右区域的磁场的磁感应强度的大小分别为B1和B2，一根金属棒ab垂直放在导轨上并与导轨接触良好，棒和导轨的电阻均不计．金属棒ab始终在水平向右的恒定拉力F的作用下，在左边区域中恰好以速度v0做匀速直线运动，则以下说法中正确的是          (  )A．若B2＝B1时，棒进入右边区域后先做根据短文内容，从短文后的七个选项中选出正确的填入空白处。选项中有两项为多余选项。Evaluating Sources (来源) of health Information Making good choices about your own health requairs reasonable evaluation. A key first step in bettering your evaluation ability is to look carefully at your sources of healthy information. Resonable evaluation includes knowing where and how to fins relevant information, how to separate fact from opinions, how to recognize poor reasoning, and how to analyze information and the reliability of sources.     小题1:   Go to the original source. Media reports often simplify the results of medical research. Find out for yourself what a study really reported, and determin whether it was based on good science. Think about the type of study.    小题2:   Watch for misleading language. Some studies will find that a behaviour “contributes to” or is “associated with” an outcome; this does not mean that a certain course must lead to a certain result.  小题3:    Carefully read or listen to information in order to fully understand it.Use your common sense. Ifa report seems too good to be true, probably it is. Be especially careful of information contained in advertisements.    小题4:    Evaluate “scientific” statements carefully, and be aware of quackery(江湖骗术).   小题5:    Friends and family members can be a great source of ideas and inspiration, but each of us needs to find a healthy lifestyle that works for us.Developing the ability to evaluate reasonably and independently about the health problems will serve you well throughout your life.A．Make choice that are right for you. B．The goal of an ad is to sell you something.C．Be sure to work through the critical questions. D．And examine the findings of the original research.E. Distinguish between research reports and public health advice.F. Be aware that information may also be incorrectly explained by an author’s point of view.G. The following suggestions can help you sort through the health information you receive from common sources.