The policeman asked the child _____ cross the street _____ the traffic lights turned green.     [ ]

A. not, when

B. don't, before

C. not to, until

D. not, until

在32×10G系统中，收端采用WPA＋WBA做预放，如果接收端OTU都采用PIN管激光器，建议不在D32的输出口与收端的OTU之间加5dB衰减，而在D32的IN口前加5dB的衰减器。