传输WDM端口利用率指在（）系统中用于开通波道或波道转接的实际物理OTU端口的利用率。
A.SDH
B.PDH
C.WDM
参考答案：C
Now the environment in city is ______ than it was before. We should keep it
clean. [ ]
A. much better
B. more worse
C. more better
D. much worse
挖孔桩锁口高度至少（）cm以上，孔口周防护栏加设安全立网，悬挂安全警示标识
A.10.0
B.20.0
C.30.0
D.100.0
