Question: What is the primary purpose of the Message Reference field in the context of Point-to-Point Short Message Service (SMS) over the mobile radio interface?
Option 1: To specify the priority level of an SMS message
Option 2: To indicate the format of the message content (e.g., text, binary)
Option 3: To link acknowledgement/error messages with their associated data/message transfer attempts
Option 4: To provide a timestamp for when the message was sent
Explanation: The Message Reference field serves as a sequence number, enabling the linking of RP-ACK (acknowledgement) or RP-ERROR (error) messages with their corresponding preceding RP-DATA (data) or RP-SMMA (message transfer attempt) messages. This linkage is crucial for ensuring reliable message exchange and handling in mobile networks, allowing for proper response to message delivery outcomes.