在声程大于3N的远场区，晶片辐射的活塞波可近似看作（）。
参考答案：球面波
_____ the city centre, we saw a stone statue of about 10 metres in height. [ ]
A. Approaching
B. Approached
C. To approach
D. To be approached
其他棉制的絮胎及絮胎制品
