Question: What triggers the measurement of 'Answered calls for the called party numbers' in a UMTS/GSM Core Network (CN) Circuit Switched (CS) domain?
Option 1: Receipt of a 'SETUP' message from the calling mobile (UE: User Equipment)
Option 2: Transmission by the MSC-S (Mobile Switching Center - Server) of an 'ALERTING' message to the called mobile
Option 3: Transmission by the MSC-S of a 'CONNECTION ACKNOWLEDGE' message to the called mobile or reception of an 'ANM' (Answer Message) or 'CON' (Connect Message) from an adjacent MSC-S for the given observed destination
Option 4: Disconnection of the call with a 'RELEASE COMPLETE' message
Explanation: This is the correct trigger as per the provided context. The measurement is specifically tied to the point when a call is acknowledged as connected, which is after the called party has accepted the call. This aligns with the transmission of a 'CONNECTION ACKNOWLEDGE' message or the reception of an 'ANM' or 'CON' message, indicating the call has been successfully answered by the destination (called party number).