Question: What triggers the network to initiate GMM common procedures?
Option 1: Receipt of UE's location update request
Option 2: Detection of UE's abnormal behavior
Option 3: Received information such as GPRS ciphering key sequence number and P-TMSI
Option 4: Expiration of UE's authentication timer
Explanation: The network initiates GMM common procedures, like identification or authentication and ciphering, based on specific received information. This includes the GPRS ciphering key sequence number and P-TMSI, which are crucial for security and mobility management in the cellular network.