问题
单项选择题
横波以波速u沿x轴负方向传播，t时刻波形曲线如图。则关于该时刻各点的运动状态，下列哪一个叙述是正确的？（）
A.A点振动速度大于零
B.B点静止不动
C.C点向下运动
D.D点振动速度小于零
答案
参考答案：D
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横波以波速u沿x轴负方向传播，t时刻波形曲线如图。则关于该时刻各点的运动状态，下列哪一个叙述是正确的？（）
A.A点振动速度大于零
B.B点静止不动
C.C点向下运动
D.D点振动速度小于零
参考答案：D
| 阅读短文，从每题所给选项中选出可以填入空白处的最佳选项。 | ||||
| Do you often think of your parents? You may say, "Of course, I __1__. I often buy presents __2__ my mother and my father on some important days." Here's a story about my friend. She works in a big city. She is very busy. So she doesn't have time __3__ her parents. But she often calls her parents. Every time, she dials (拨) the number, but then she puts down the telephone. __4__five minutes, she dials the number again. Later, I ask, "Why do you dial the number __5__ ?" She smiles, "My parents are __6__ and slow. They can't get to the telephone quickly. I always do so when I call them. I only want to give them __7__ to answer the telephone. My friend is a good girl. She is always __8__ of her parents. You also want to be a __9__ child, right? Please always remember (记住) to __10__ your parents in every situation (在各种情况), not just on some important days. | ||||
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