问答题

浅海传播损失的分段表示为( )。

A.近距离，球面扩展衰减
B.中等距离，3/2次方规律扩展衰减
C.远距离，柱面扩展衰减
D.任意距离，柱面扩展衰减

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Maggie Walker was born in 1867 in Richmond, Virginia. Her mother was once a slave in a rich woman's house. When Maggie was very young, a thief killed her father. Her family was impoverished, so Maggie's mother started doing laundry in her home. Maggie had to help her. She washed clothes every day, but she continued to go to school. She was a very good student, especially in math.

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近距离处潜艇目标强度测量值有可能小于远距离处目标强度测量值，原因是( )。

A.近距离传播衰减小
B.远距离传播衰减大
C.换能器的指向性
D.近距离处，回声强度不同于点源的衰减规律