A.同時(shí)傳遞數(shù)據(jù)語(yǔ)音且上下數(shù)據(jù)帶寬對(duì)稱 B.同時(shí)傳遞數(shù)據(jù)語(yǔ)音且上下數(shù)據(jù)帶寬不對(duì)稱 C.只傳數(shù)據(jù)上下對(duì)稱 D.只傳數(shù)據(jù)上下不對(duì)稱