摇表测量绝缘电阻时，摇动手柄的转速应保持在（）r/min，直至表针稳定时读出数据。
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Which of the following statements regarding ISDN are correct?（）
A. Each ISDN B channel has transmission speeds of up to 64 kbps.
B. The ISDN B channel can carry video, voice or data.
C. The ISDN B channel transmission rate varies depending on the service used.
D. The ISDN D channel transmits control information.
E. The ISDN B channels can be configured with different subnets and encapsulation types when dialer profiles are configured.
不正确的采样，事后会很难察觉和检查，而且很难补救。
A. 正确
B. 错误
观看文艺演出或体育比赛时，为表热情，掌声越多越好。
A. 正确
B. 错误
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