Question: What action does a receiving AM RLC entity take when it receives an AMD PDU from the lower layer, containing byte segment numbers y to z of an RLC SDU with SN = x, and the byte segment numbers have been received before?
Option 1: Forward the AMD PDU to the higher layer for immediate processing.
Option 2: Discard the received AMD PDU due to duplicate byte segments.
Option 3: Buffer the AMD PDU and send an acknowledgement for the duplicate segments.
Option 4: Split the AMD PDU into new segments to retransmit the non-duplicate parts.
Explanation: According to the specified RLC protocol behavior, if byte segment numbers y to z of the RLC SDU with SN = x have been received before, the receiving side of an AM RLC entity shall discard the received AMD PDU. This ensures efficiency by not processing duplicate data and minimizes unnecessary buffer usage.