货机：卫星通信系统中，哪一个部件是货机独有的？
ATop mounted high gain antenna (HGA)
BSatellite data unit (SDU)
CSatellite data unit configuration module (SCM)
DLow noise amplifier/diplexer (LNA/DIP)
ATop mounted high gain antenna (HGA)
BSatellite data unit (SDU)
CSatellite data unit configuration module (SCM)
DLow noise amplifier/diplexer (LNA/DIP)