【单选题】一个弹簧振子放在光滑的水平桌面上,第一次把它从平衡位置拉开d,释放后,它作简谐振动,振动的频率是f 1 ,第二次把它从平衡位置拉开3d,释放后,它仍作简谐振动,振动频率是f 2 ,这两次振动频率的比值 是( )。
【单选题】制造商在同一区域市场内各个层次的中间环节中,选择少数中间商来推销其商品的销售策略是:
【单选题】I can speak Chinese, but I ____ speak English. [ ]
【单选题】Nina doesn’t speak Thai. She is asking Rick, “Will I ?”
【多选题】一个弹簧振子,在光滑水平面上做简谐运动,如图所示,当它从左向右恰好经过平衡位置时,与一个向左运动的钢球发生正碰,已知碰后钢球沿原路返回,并且振子和钢球不再发生第二次碰撞.则下面的情况中可能出现的是()
【简答题】A.He doesn't think they are allowed to speak. B.He doesn't know what's happening outside. C.He was only talking to himself. D.He thinks it's too noisy to talk now.
【简答题】A.The woman doesn't like the man. B.The man tries to speak more loudly. C.The man doesn't want to speak up. D.The woman has no problem hearing the man.