单项选择题
A.10-20minB.20-30minC.30-40minD.40-50minE.50-60min
A.10HzB.20HzC.50HzD.30HzE.40Hz
A.< 0.05TB.< 0.02TC.>0.2TD.0.1-0.2TE.0.05-0.1T