Which statement best describes echo?（）
- AEcho is the discernable leak-through of your own Rx path into your own Tx path.
- BEcho is the discernable leak-through of the packets of your Rx path into your own Tx path.
- CEcho is the nonaudible leak-through of the packets of your Rx path into your own Tx path.
- DEcho is the audible leak-through of the packets from the transmit path into your own receive path.
- EEcho is the nonaudible leak-through of the packets of your Tx path into your own Rx path.