Question: In a Voice Group Call Service (VGCS) scenario, what triggers the anchor MSC to terminate a call when the pre-set "no activity" timer expires?
Option 1: Receipt of a new voice packet from any participant
Option 2: Expiration of a separate, overall call duration timer
Option 3: Detection of no activity (as defined by specific criteria related to activity) within the pre-set time
Option 4: Manual termination request from the group call initiator
Explanation: The correct answer is Option 3 because, according to VGCS specifications, the anchor MSC terminates the call when it detects no activity (as defined by specific criteria related to activity) within a pre-set time, which is determined by the "no activity" timer. This mechanism ensures calls are not indefinitely left open due to inactivity.