单项选择题
A.550.02 B.564.48 C.582.23 D.593.52
A.8.820kHz±0.1kHz B.7.820kHz±0.2kHz C.5.820kHz±0.1kHz D.4.820kHz±0.2kHz
A.5 B.8 C.10 D.12
A.12.0~17.0 B.15.0~20.0 C.17.0~21.0 D.20.0~23.0
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