如图所示，在倾角为α的传送带上有质量均为m的三个木块1、2、3，中间均用原长为L、劲度系数为k的轻弹簧连接起来，木块与传送带间的动摩擦因数均为μ，其中木块1被与传送带平行的细线拉住，传送带按图示方向匀速运行，三个木块处于平衡状态。下列结论正确的是（）
A.2、3两木块之间的距离等于
B.2、3两木块之间的距离等于
C.1、2两木块之间的距离等于2、3两木块之间的距离
D.如果传送带突然加速，相邻两木块之间的距离仍不变
参考答案：B, D
阅读短文， 从方框中所给的四个句子中选出正确选项， 填在短文空缺处，使短文内容完整、连贯。  Do you have a mobile phone? Do you often send text messages（信息）to your friends of family? If you keep sending text messages over and over again, there may be something wrong with your fingers(手指). 小题1: If you don’t , you may get hurt one day. Text messaging or “texting” is becoming popular. But , scientists have found out that texting can give us problems with fingers. Too much texting can make your fingers uncomfortable. When we press small buttons over and over again , we may have a disease(疾病) called RSI. RSI is short for Repetitive Strain Injury(重复性力损伤). Harriet Wilson is a doctor. She has many patients(病人) with RSI.小题2: If we spend more than 10-15 minutes every day, we could have such problems in the future. Mobile phones and the buttons are getting smaller and smaller. 小题3: Texting with a smaller phone is worse than using a large phone with bigger buttons.小题4: . It’s easy to type with a large one. If you use a computer keyboard and play video games for long, you may have the same problem. More and more people can find themselves with RSI.
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