Question: What is the primary purpose of the Reply Path mechanism in the Short Message Service (SMS)?
Option 1: To enable prioritized message delivery for emergency services
Option 2: To facilitate billing for SMS transactions between operators
Option 3: To ensure a service centre's commitment to deliver a reply from the replying Mobile Station (MS) to the originating Short Message Entity (SME)
Option 4: To enhance encryption for secure message transmission
Explanation: The Reply Path mechanism guarantees delivery of a reply, if requested and supported, from the replying Mobile Station to the originating Short Message Entity, ensuring responsiveness across different configurations. This is its core function in SMS service functionality.