Which three statements about end-to-end delay are true？ （）
- A End-to-end delay is the sum of propagation delays， processing delays， serialization delays， and queuing delays.
- B Coast-to-coast end-to-end delay over an optical link is about 20 ms.
- C Processing delay depends on various factors， which include CPU speed， CPU utilization， IP switching mode， and router architecture.
- D Propagation and serialization delays are related to the media.
- E Propagation delay is the time it takes to transmit a packet and is measured in bits-per-second （bps）.
- F Serialization delay is the time it takes for a router to take the packet from an input interface and put it into the output queue of the output interface.