A.定時(shí)的專(zhuān)用電路B.雙向多點(diǎn)專(zhuān)用電路C.廣播多點(diǎn)專(zhuān)用電路D.單向多點(diǎn)專(zhuān)用電路
A.EDIB.EmailC.SOSD.POS
A.2.3B.2.5C.2.8D.3.4