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阅读表达 阅读下面短文，根据其内容完成后面各项任务 It’s difficult when you have no good friends around - maybe because you have moved to a different school or a different class or you re sick at home.没有朋友你也许会感到寂寞。You want to have new friends. But how to make them? How do you start? How do you get along with people? Here are five ways to help you to do these. Greet(闾候)people Greet people and hope that they have a good day - whatever time of day it is.  It doesn’t hurt any people. It also makes people think you’re friendly. Share 如图所示，质量为M的长木板静置于光滑水平面上，一质量为m的小铅块（可视为质点）以水平初速v由木板左端滑上木板，铅块滑至木板的右端时恰好与木板相对静止，此时，它们共同的速度为vt．已知铅块与长木板间的动摩擦因数为μ，木板长为L，在此过程中，木板前进的距离为s．则在这个过程中铅块克服摩擦力所做的功等于（ ）A．μmg sB．μmg LC．μmg（s+L）D．