问题
选择题
| 关于多普勒效应，下列说法中正确的是（ ） A．只要波源在运动，就一定能观察到多普勒效应 B．当声源静止、观察者运动时，也可以观察到多普勒效应 C．只要声源在运动，观察者总是感到声音的频率变高 D．当声源相对于观察者运动时，观察者听到的声音的音调会变高 |
答案
答案：B
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| 关于多普勒效应，下列说法中正确的是（ ） A．只要波源在运动，就一定能观察到多普勒效应 B．当声源静止、观察者运动时，也可以观察到多普勒效应 C．只要声源在运动，观察者总是感到声音的频率变高 D．当声源相对于观察者运动时，观察者听到的声音的音调会变高 |
答案：B
| 完形填空。 | ||||
| June 1 a sister. Her name is Lisa. They are Chinese. June is seven and Lisa is nine 2 old. June's birthday is July 21st. Lisa was born (出生) 3 July, too. Now they are in the same school. They usually go to school 4 seven o'clock in the morning. Lisa's 5 subject is English and she 6 English very well. June can play the guitar. So she wants 7 the School 8 Club. After school June likes to play chess 9 Lisa. They often go to 10 on weekends. | ||||
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