题目

如图所示，一列简谐横波沿x轴正方向传播，实线表示t=0时刻的波形，虚线表示t=0.7s时刻的波形。则这列波的 A．波长为4m B．周期可能为0.4s C．频率可能为0.25Hz D．传播速度可能约为5.7m/s 答案：AB           短文改错 　　　Mary had a nice white lamb and loves it very much． 　　 　　1．______ 　　 　　 She kept it tying to a tree during the day and went 　　 　　 2．______ 　　 　　 to bring it every evening．One day, but, the lamb was 　　 　　 3．______ 　　 　　 missed．She found his neighbour, Aleka, had suddenly 　　 　　 4．______ 　　 　　 got a new lamb, so she immediately went to his house． 　　 　　 5．______ 　　 　　 Aleka explained her his lamb was black．While they were 　　 　　 6．______ 　　 　　 talking, it began to rain．So Mary stayed in her house 　　 　　 7．______ 　　 　　 as the rain stopped．When she went out, she was happy 　　 　　 8．______ 　　 　　 to find that the little lamb was almost white．It's 　　 　　 9．______ 　　 　　 wool, dyed black, had been washed cleanly by the rain． 　　 10．______