Question: Which of the following warning services, utilizing the same Access Stratum (AS) mechanisms as Commercial Mobile Alert Service (CMAS), is specifically characterized by the distinction between primary and secondary notification messages based on delivery delay stringency?
Option 1: Earthquake and Tsunami Warning System (ETWS)
Option 2: Cell Broadcast Service (CBS)
Option 3: EU-Alert
Option 4: Emergency Alert System (EAS) over CMAS-like AS mechanisms
Explanation: ETWS (Earthquake and Tsunami Warning System) is the service that distinguishes between primary notifications, which have stringent delivery delay requirements, and secondary notifications. This distinction is specific to ETWS among the listed options, highlighting its unique operational requirements for urgent alerts.