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声音的特征

> 下列说法正确的是（　　） A．一杯水去掉一半斤，剩下部分密度也减半 B．由表达式R=U/I可知导体两端所加电压为零，电阻也为零 C．同步通讯卫星在近地点机械能减小，远地点机械能增大 D．可变音调的口哨在振动的空气柱变短时，其音调变高

问题：

发布时间：2024-09-12

下列说法正确的是（　　）

A．一杯水去掉一半斤，剩下部分密度也减半

B．由表达式R=U/I可知导体两端所加电压为零，电阻也为零

C．同步通讯卫星在近地点机械能减小，远地点机械能增大

D．可变音调的口哨在振动的空气柱变短时，其音调变高

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