Select a key benefit of DSL.（）

• A、TCP packet sizes can be optimized by the router so there is no IPSec or AAL5 padding.
• B、The local loop is a dedicated connection for a single subscriber to the DSLAM. 
• C、Access to the WAN media uses a poll/response mechanism so no two subscribers transmit at the same time. 
• D、There are no distance requirements from the Central Office (CO).