Click the Exhibit button. When designing a DWDM system with multiple amplified spans, a pre-amp is needed at Site B to （）. (Choose three.)

• A、offset the OADM loss at site b 
• B、overcome the high multiplexer loss at site a 
• C、amplify signal levels after the high loss through Fiber Span 1
• D、adjust add channels at site B to be at the same level as the passthrough channels
• E、ensure that the per channel power is higher than the minimum needed for the post-amp at Site b