48.下列何者是 ATM 採用的多工技術？ (A)分頻多工(Frequency Division Multiplexing, FDM)(B)分碼多工(Code Division Multiplexing, CDM)(C)同步分時多工(Synchronous Time Division Multiplexing, Synchronous TDM)(D)非同步分時多工(Asynchronous Time Division Multiplexing, Asynchronous TDM)