单项选择题
A.黑、红、紫 B.红、紫、黑 C.黑、紫、红 D.红、黑、紫
A.1300nm B.1310nm C.1550nm D.1625nm
A.0.21dB/km B.0.22dB/km C.0.27dB/km D.0.36dB/km