单项选择题
A.95% B.96% C.98% D.100%
A.90% B.93% C.85% D.94%
A.超短期 B.短期和超短期 C.中期 D.长期
A.20~20000HZ B.20~3400HZ C.300~3400kHz D.3.4~20kHz
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