Question: What determines the actual MAC-d PDU size when 'Flexible MAC-d PDU Size' is used for E-DCH in a UTRAN Iub interface?
Option 1: Maximum MAC-d PDU Size Extended IE of E-DCH Logical Channel Information IE
Option 2: MAC-d PDU Size List IE of the E-DCH Logical Channel Information IE
Option 3: Specifications for Common Transport Channel data streams
Option 4: Node B Application Part (NBAP) signalling configuration
Explanation: When 'Flexible MAC-d PDU Size' is utilized for the E-DCH, the actual size of the MAC-d PDU is determined by specific rules outlined in technical specifications for efficient resource use without exceeding the defined maximum PDU size.