单选题

In order to maintain the reach of a typical 100G WAN transport system(~1500km), several system improvements have to be made to recover the lost(     ),including the use of low-loss low-nonlinearity(     ),Raman amplification, and stronger error correction. 

单选题
【正确答案】 B
【答案解析】
单选题
【正确答案】 A
【答案解析】