A.1倍B.2倍C.5倍D.10倍
A.20-15000HzB.16-15000HzC.20~20000HzD.小于20000Hz
A.黑底黄字比黑底蓝字更易识别B.黑底蓝字比黑底黄字更易识别C.黑底蓝字和黑底黄字识别度差不多D.黑底蓝字和黑底黄字识别度不可比