What best describes RADSL?

A.
The DSL line trains at the highest rate possible, limited mainly by line conditions and provisioning options.

B.
The DSL line rate (bandwidth) is automatically increased when data queues are filled to a predetermined threshold.

C.
The DSL line rate remains constant while noise margins are automatically adjusted.

D.
The DSL modems detect the presence of CAP, DMT, SDSL, or G.SHDSL modulation at the receiver input and automatically select the appropriate mode to transmit.