Question: In the UTRAN Iub interface, what determines the actual MAC-d PDU size when 'Flexible MAC-d PDU Size' is used for HS-DSCH?
Option 1: SID IE and MAC-d PDU Size IE of MAC-d PDU Size Index IE
Option 2: Maximum MAC-d PDU Size Extended IE alone
Option 3: A fixed size defined in the Node B configuration
Option 4: Specifications for dynamic handling of packet sizes, ensuring optimized data transmission
Explanation: When 'Flexible MAC-d PDU Size' is utilized for HS-DSCH, the actual MAC-d PDU size is determined through specifications that ensure dynamic handling of packet sizes to optimize data transmission over the UTRAN Iub interface.