题目

—Got your driving license? —No. I _____ too busy to have enough practice, so I didn’t take the driving test last week. A. will be                                   B. am                          C. have been                D. had been 答案：D 解析: 略如图所示为一列沿着x轴正方向传播的简谐横波在t=0时刻的波形图。已知这列波的波速v=5.0m/s。则 A．这列波的频率f=1.0Hz B．经过一个周期，x=0.5m处的质点沿着x轴正方向运动的距离为l.0m C． x=0.5m和x=lm处的质点可以同时到达波峰位置 D．在t=0.5s时刻，x=0.5m处的质点正在沿着y轴负方向运动